"Funny Aneurysm" Moment: in episode 10 of the anime, Nimura invites Miu out on a date. The same thing happens in the Shoujo manga, except Miu's classmates have spotted them, and is now planning to use that information to get Miu in trouble.
Mexicans Love Speedy Gonzales: Miu is very popular in Russian fandom, more than any other of the characters for quite obvious reasons, despite the fact that she is depicted as a typical foreigner girl in anime.
Narm: The family ties between the heroes are rather complicated and difficult to explain to outsiders. Just imagine that Hina is the niece of Yuuta and the younger sister of his wife Sora, despite the fact that he and Sora are not related to each other.
Strangled by the Red String: Anime falls into this, as the TV series actually ends before the official couple appears, and OVA after it.
WTH, Casting Agency?: Sumire Uesaka is assigned to voice the main character, not her half-russian younger sister, despite the fact that Sumire professionally speaks russian and studied Russia at the university.