Chikan Saresou ni Natteiru S-kyuu Bishoujo wo Tasuketara Tonari no Seki no Osananajimi datta / Я спас красивую девушку от насильника, а она оказалась моей подругой детства

When Ryou Takamori confronts a groper on the train, it turns out he's come to the rescue of his estranged childhood friend, Hina Fushimi. The two drifted apart in middle school as the social gap between ever-popular beauty Hina and plain loner Ryou widened—but this incident might be the catalyst Hina's been waiting for to rekindle their friendship. And she's got her fingers crossed that it'll spark something more...if only Ryou would get a clue!

(Source: Yen Press)