1) カイ, 2) なつ・かしい, 3) なつ・かしむ, 4) なつ・く, 5) ふところ - feelings, yearn for, miss (something)
懐かしいnatsukashii - remember sweetly, long for, miss (something) 懐古kai ko - nostalgia, reminiscence 懐中時計kai chuu do kei - pocket watch 懐妊kai nin - pregnancy (used with very erai people)