To be completely honest, having Japanese partner is absolutely helpful. I know tons of people who date with the other ethnicity just to learn their languages. I personally think it's not a healthy relationship. So you shouldn't manipulate someone's feelings.

Useful apps for iOS are: iKana - to learn Kana iKanji - to learn Kanji Human Japanese - to learn Japanese sentence structure, it is basically a textbook but as an app. It also has quizzes at the end of each chapter and is also available on android Cram - it is a flashcard app. Flashcards are the number 1 resource for learning a language. You can use them to remember any aspect of Japanese and are especially useful for learning/remembering vocabulary when you have spare time or you are waiting for something.

As book i can recommend : "minna no nihongo" , it's really very useful ...