|Height||4'11" (152 cm)|
|Birthdate||May 23 (Gemini)|
|Year||1st year in high school|
|Affiliation||Minegahara High School|
|Light Novel||Volume 1|
|Japanese Seiyuu||Nao Tōyama|
|“||I want everyone to like me. Or rather, I don't want them to hate me.||”|
— Tomoe Koga
Tomoe Koga (古賀 朋絵, Koga Tomoe) is one of the main characters of the Seishun Buta Yarou wa Bunny Girl Senpai no Yume wo Minai series. As a result of Adolescence Syndrome, Tomoe is capable of eliciting simulated future events.
Tomoe is a short girl who has fluffy light-brown hair styled into a bob-cut along with blue eyes. The left side of her hair is adorned with a T-shaped hair barrette.
Sakuta has remarked on multiple occasions that she has a large butt, which bothers her.
Tomoe has a strong desire to fit in and avoid being shunned, which is why she bears unease over her past and why she cares about her social life and status; the latter is why she is usually seen on her phone and why she was unable to respond to Yosuke Maezawa's advances. After her experience with Sakuta, she was able to learn not to focus so much on what others think of her and thanked him for helping her grow as a person.
She has an odd sense of ethics, as immediately after she realized her mistake for kicking Sakuta, she ordered him to kick her in return so that they would be even.
During her time in a middle school in Fukuoka, Tomoe was a bumpkin who hung out with an unnoticed group in her class. However, her father was relocated, which forced her to move to Tokyo. Fearing she would be considered uncool and get bullied, she began wearing makeup, styled her hair in a fancy salon, and wore clothes from fashion magazines. She became satisfied with the result.
Tomoe encountered Sakuta Azusagawa at a playground and kicked him to defend a little girl, thinking he was a pedophile. After Sakuta cleared up the misunderstanding, she demanded he kick her in return so they would be even. Unfortunately for both of them, a nearby police officer witnessed the obscene act and they were subsequently given a lecture at the police station; Tomoe unknowingly made things more difficult by constantly checking her phone.
On June 27, Tomoe found herself being asked out by Maezawa, but felt too uneasy to give him a definite reply. Unbeknownst to her, Tomoe's Adolescence Syndrome rewound time so that the events of June 27 repeated itself. After the third time the day was rewound, she was found hiding in a classroom podium by Sakuta. Once they learned both of them had been living the same day three times, Tomoe revealed to Sakuta that her friend Rena Kashiba had a crush on Maezawa, but the latter had developed eyes for Tomoe. She further disclosed that she did not want to accept Maezawa's proposal, but was unable to at the risk of being shunned by her class. Unfortunately, a brief moment of panic makes them fall over into an unintentionally obscene position, disgusting a passing Maezawa and subsequently Mai Sakurajima.
Later that day, Tomoe was hired at Benny's and was surprised to see that Sakuta worked there as well. After closing time, Tomoe attempted to get Sakuta to keep up the implication that they were dating, but failed. However, upon revealing that she did not want to look like she was lonely, Sakuta agreed to keep up the lie. Tomoe then asked Sakuta to go on a date with her tomorrow after his shift at work is over, so that she could tell Rena that she went on one.
The next day, Tomoe went with Sakuta to the aquarium, where she marveled at the various displays. While watching one particularly featuring penguins, she compared herself to a penguin who always followed the group. However, after comparing Sakuta to the penguin being laughed at, she became troubled. The pair then went outside, where Tomoe revealed that she used to be a socially awkward person. In response, Sakuta told her not to be bothered over who she was before, as she liked the person who she was now, which Tomoe happily agreed with. The two noticed one of Tomoe's classmates named Nana Yoneyama at a beach and learn she was looking for her phone strap. Tomoe managed to find it for her near the edge of the shore, but fell into the water, which caused her to get sick the next day.
While resting in the nurse's office, Tomoe asked Sakuta why he went along with her requests, to which he replied that she was desperate when she asked. Tomoe stated that she was worried about the school's opinion of her, explaining that she doesn't want everyone to hate her. Sakuta responded by stating that he would be satisfied if he had only one person who liked him, which intrigued Tomoe.
Later on, Tomoe gave Sakuta a can of peaches as a gift of gratitude, but was flustered and provoked once Sakuta compared the peaches to her butt. Later at work, she was surprised that Mai had not rejected Sakuta yet. Upon hearing from Sakuta that he and Mai would have dated if it weren't for the time loop, Tomoe asked in disbelief if Mai had stated her love for him. The reply was a no, and Tomoe proclaimed he was just saying things.
On July 7, Tomoe was found by Sakuta sitting by herself in the train station, feeling down as a result of a rumor that she was a promiscuous girl. However, once Maezawa made a derogatory remark at her, Sakuta swiftly beat him to the ground with a kick and stomped on his face; proclaiming that he stepped on feces beforehand, and mocked his way of life while declaring himself a virgin. She is subsequently ushered away from the station by Sakuta, where they laughed at the fact that Sakuta didn't care if he went too far.
Later at the beach, Tomoe stated that she had an idea of what he meant by having one person who needed him, adding that she felt like she was his girlfriend. Tomoe then disclosed that she was a virgin, earning a fit of laughter from Sakuta, who told that he wouldn't have believed the rumor at all. As the two walked along the shoreline, Tomoe asked how she would pay him back, to which he replied that she would be his friend once the lie that they were dating ended. In response, she announced she would be his best friend instead. At her home that night, Tomoe came across an online advertisement featuring Mai, and gazed at it sadly.
On July 17, Tomoe went to buy a swimsuit along with Sakuta. Later that evening, Tomoe explained that as a believable way to break up the relationship, she thought of a scenario where Sakuta never got over Mai, and added that they would have the "argument" on their way back from the beach date.
The following day, Tomoe met up with Sakuta at the train station, where she noticed Sakuta lewdly observing her. At the beach, they spent their date splashing each other with water, having a sandcastle contest and drinking slushed ice drinks. As the sun began to set, while sitting on the beach shore with Sakuta, Tomoe thanked him for everything and proclaimed the end of their "relationship". Before they went home, Tomoe stated that she hoped he would go out with Mai someday. However, time was rewound back to the morning of July 18.
That morning, Tomoe was questioned by Sakuta if she had experienced a time loop. In response, she claimed that she did not experience a time loop before waving him off. Later on, the two repeated their date and goodbye as it occurred previously. Still, July 18 occurred a third time to repeat the same events; once again, after she ended their false relationship, she rewound July 18 a fourth time. Tomoe was mildly surprised when Sakuta announced they were heading to Enoshima, but went sightseeing with him there regardless. Once they were on a wooden bridge, Sakuta told her to stop lying, and that no matter how many times she rolled the dice, his feelings wouldn't change. Tomoe denounced Sakuta as a liar, responding that feelings do build up the more they are repeated; at least for her. She explained that she tried to forget their experiences, couldn't bring herself to. However, with some indirect encouragement from Sakuta that nothing would change, Tomoe was able to loudly declare that she loved him, before crying with profound sorrow. Now able to come to grips with reality, time rewound all the way to the morning of June 27, revealing that everything that had happened since June 27 was a simulated future.
Unlike the initial June 27, Tomoe was able to reject Maezawa, claiming that she had feelings for someone who didn't have a smartphone. After coming across Sakuta, she stated that Rena would hate her for rejecting him and that she wouldn't have a place in her class; Tomoe clarified that Sakuta had turned her into a better person. Sakuta promised that no matter what happened, he would always be her friend, to which she playfully responded that she was the one who allowed him to be a close friend. Tomoe was later found walking alone outside the school, but she came across some students who wanted to hang out with her and walked with them.
- Main article: Adolescence Syndrome
Stemming from her desire to fit in, Tomoe was capable of evoking a simulated future in which she could rewind and restart the current day. After professing her love to Sakuta, while also acknowledging she could only be friends with him, time was reset to before the simulated future was elicited.
Tomoe admired Sakuta's decision to publicly confess his love toward Mai Sakurajima and started viewing him as an individual "who came full circle and acceptable". As such, she confided her anxiety over Maezawa's advances to Sakuta and was willing to keep up the lie that they were dating. After witnessing Sakuta stand up for her against Maezawa, she proclaimed that they would be best friends after the first term.
However, her feelings toward Sakuta were more than just platonic, as she became saddened upon seeing an online ad featuring Mai Sakurajima. Near the end of a repeated July 18 within her elicited future, Tomoe admitted that she had feelings for him and did not want to end their fake relationship together. After she came to grips with the fact that he only had feelings for Mai, she ended her evoked future to allow the events of June 27 to pass, and is content with just being a close friend.
Tomoe is friends with her at school and wants to fit in with her and the rest of her group.
- Some official illustrations of Tomoe depict her with a pair of demonic wings and a demon's tail, which references her being "Laplace's Demon".