I can definitely see the similarities to Bakemonogatari and Sakurada Reset here, and that, readers, is not a bad thing, at least for me. Both of those shows could subvert the concept of a Tsundere Girlfriend or Jealous Little Sister without breaking a sweat, and so too does Bunny Girl.
In a lazier anime, agreeing to fake-date a kohai would land Sakuta in some seriously warm water, but after he explains everything properly to Mai, she withholds punishment, claiming that’s its own punishment, but really it’s a gesture of trust. Sakuta was the one and only person who never forgot her, after all (except for one brief period).
As with Araragi Koyomi, Mai can see her would-be-boyfriend is trying to help someone in need, and doesn’t judge that someone’s choices that led to them needing help. Instead she gives Sakuta her blessing, serves as the first person other than him to interact with his shut-in sister, and then bids him a good night.
However, she does warn him not to let “pretend” turn into “serious”—not to betray the trust she’s putting in him—and he laughs it off too casually for her taste, as well as mine.
The next day Sakuta is ready for his fake date with Koga Tomoe. She’s late, yawns on the train, and can’t keep her hands off her phone (he has neither smart nor flip, the damn hipster).
When she lists the reasons for her fatigue (group chatting till 2AM; watching funny animal videos; preparing for the date “a bit”), Sakuta starts to get to the root of Koga’s frustration that led to her becoming an all-seeing, all-knowing Leplace’s Demon: She must be informed. She must join in on the conversation. She must be liked, and not seen as a loner or weirdo.
This point is driven home at the aquarium as they watch penguins: she deems Sakuta to be the penguin whom the others laugh at but doesn’t care, while she’s the penguin who follows the others in lockstep. Later, Sakuta gets more insight: Tomoe was once a “country bumpkin” from Fukuoka (hence her adorable lapses into drawl), but began a regimen of thorough reinvention and improvement to become the stylish and proper-speaking person she is.
Sakuta can surmise that she feels guilty about “abandoning” the person she is and wondering whether who she is now is who she really is, but he considers that kind of thinking “immature.” He assures her that who she is now is who she is; the culmination of choices she made and hard work she undertook. It’s nothing to be ashamed of.
Sakuta also shows Tomoe a few things, such as when they spot a classmate of hers from a group further down her class’ pecking order. The two of them help this classmate find a strap she lost on the beach, despite her feeling “unworthy” of someone of Tomoe’s stature wasting their time on her. Sakuta isn’t the kind of person who ranks people by their social stature; all are equal as long as they are virtuous.
When Tomoe catches a cold from falling into the water and spends a day in the nurse’s office, she asks Sakuta why he’s gone along with her “unreasonable” requests. He states it’s because she seemed desperate when she asked. Their differences in how they see the world are laid bare: she wants everyone to not hate her, while he wouldn’t mind if everyone hated him as long as there was One Person who needed him.
That one potential person Mai checks in with Sakuta on his land line phone, and he is honest about having enjoyed his “date” with Tomoe. Her nonverbal response is an enigma; is she intrigued; disappointed; neutral? She’s in Kagoshima on a TV shoot, and casually asks him to “bolt out of his house” to see her, but he doesn’t.
Futaba (who has unrequited feelings for his friend Kunimi) tells Sakuta that since Tomoe is satisfied with her current condition, there’s no need to relive it; the “demon” has found its desired path. Kunimi’s girlfriend Kamisato once again confronts him about spending time with her squeeze. Kamisato is another who only sees a ranking number hovering over someone’s head; if it’s not high enough, she wants nothing to do with them.
Sakuta tells Kunimi about the second fight picked by Kamisato, and it leads to Kunimi informing him of untoward rumors about Tomoe being loose/easy. Despite Tomoe’s efforts and veneer of satisfaction, her relationship with Sakuta has brought a different kind of unwanted attention. When Mai leaves a message on Sakuta’s phone, he moves to call her back, but stops. He has work to do.
Again, like Koyomi of the Monogatari series, Sakuta is going to perform the task he volunteered for to the best of his ability. He may not be the strongest or smartest, but that doesn’t mean he can’t outsmart someone who can easly outstrong him. As Tomoe already starts feeling the fallout by being left out of her friends’ conversation, Sakuta puts his plan into action.
That plan is nothing more than defending the honor of someone who doesn’t deserve the nasty rumors being told about her. He does so by letting the jock (who I believe originally tried to ask her out) come to him, provoking him into punching him, then getting back up, presenting himself as someone ready to throw hands, then kicks him hard in the shin.
The jock protests that Sakuta isn’t being “fair”, but…c’mon; pot, meet kettle! Sakuta ensures the exchange takes place on the train platform where the maximum number of peers watch how pathetic the jock is, giving him the negative attention he foisted upon Tomoe and then some.
In that moment, Sakuta was Tomoe’s boyfriend. She felt it; and surely he felt it too. They may not have spend much time together, but they both have a pretty good idea of who one another are. At her darkest hour, when it seemed everyone was ready to hate her (and indeed when it seemed she’d reset time to before this all happened), he was that One Person for her.
The person who’d go maybe too far to help her. The person she needed. You know…a friend! Hell, he announced in front of half the school he was a virgin for her sake. He’s a stand-up dude, and she couldn’t be blamed for falling for him right then and there.
Whether that’s precisely what happens, it’s without doubt a nudge in that direction; two people becoming a little closer through shared experiences, the most recent of which were fraught enough to require him to take her by the hand and run away, and the adrenaline of which caused them both to laugh uncontrollably as they ran.
Tomoe now understands a little more what Sakuta meant about his “One Person” position, and asks how she can repay him. Sakuta—ever classy yet also a bit arrogant—tells her she can be his friend “when all the lies are over.” The thing is, the lies may already be over, and Tomoe may just want something more than a friend. Why else would she frown at the sight of one of Mai’s TV commercials on her phone?
As for Sakuta…while he fought hard for Tomoe, there’s no overt indication he’s doing anything more or less than what he deems to be his duty, as he promised to be her boyfriend for the first term. As such, Mai may not have anything to worry about.
But he got awfully into the role on that train platform. He showed Tomoe that she only needs one person, and so far that one person is him. Can Mai—can we—trust that he’ll be able to extricate himself from a Leplace’s Demon so satisfied with him as her boyfriend?