If you go for strategy of Japanese lessons, at least do it right. You need some goal other than tutor sessions going hentai, such as passing some sort of exam. You should know that chances are probably much higher than 2 put of 3 that you gonna get tutorials from her brothers instead. For FO, this strategy sound very cheesy and transparent. You need consider that family, they in strange environment and all they really certain of right now is their own family. They likely a bit more strict than usual (as in, in Japan) and they gonna be weary for odd requests like "please teach me some japanese."

Also the mentioning random Japanese quotes, better to leave it until they invited you for a drink or something like that. Only then is there room for you to show off and impress. Otherwise it just awkward.

This not helping you very much, no? Frigid Onanoko being such a bummer now (nyah!) Cannot really help you. Obviously they are neighbours, so every now and then there should be neighbourhood parties or community meetings. Perfect reason to invite them for that and get to know them. This most appropriate thing FO can come up with, sorry it not very much.

saying bye now!