i really like that kazuaki was the one who brought up living together. at the beginning kira was the one pushing the relationship. we get to slowly see the dynamics of their relationship changing. the part where kazuaki goes with kira to the hospital shows how they've become equal partners. but i still think that kazuaki asking to live together is the best. it's something that he is taking the initiative to do and he's doing it for himself rather than reacting and being pushed or pulled by kira.
I really love the weird idiotic mundane ways they say their love. "i'll let you pick my scabs" "please trim my hair"