誠心 せいしん誠意 せいい
seishinseii

Noun
Adverb
no-Adjective

1. in all sincerity; with one's whole heart; whole-hearted devotion

Yojijukugo
かれ誠心 せいしん誠意 せいい、彼女 かのじょ くした。
karewa sēshinsēi kanojoni tsukushita.
He devoted himself whole-heartedly to her.