誠心誠意せいしんせいい Adverb Noun Noun English jmdict 1 adverb (fukushi)noun (common) (futsuumeishi)nouns which may take the genitive case particle 'no' yojijukugo in all sincerity;with one's whole heart;whole-hearted devotion 彼は誠心誠意、彼女に尽くした。 He devoted himself whole-heartedly to her.
Shirabe