I REALLY like that for once the girl has the hots for a boy around her age instead of the usually much manlier / overly dominant archetypes (dependable/playboy/muscular). Maybe not the most realistic but certainly refreshing, even pure (the love sure feels more genuine when the other party has little to offer).
Also p.12-13 how he doesn't want to force himself on her and gets her to confess out loud to feel her consent. It's so unexpected to witness another outcome than don't make a lady say it or she'll surrender soon enough you'd think the author is attempting to break a taboo.
And yes, Nao is love. Amazing work on various levels. Will follow Tachiroku more closely.