愉快
ゆかい · yukai · JLPT N3 · na-adj
pleasant
🎉 愉 joy + 快 cheerful = pleasant; sounds like you-kay, as in you're okay
Both kanji carry the 忄 heart radical, so the word is literally two happy hearts. 快 also means quick, as in a light, quick heart. Chinese uses the same word, 愉快 yúkuài, for cheerful.
快 — heart radical 忄 + 夬 (phonetic)
快 is a semantic-phonetic compound. The heart radical 忄 carries the meaning, since the original sense referred to a feeling of pleasure or delight. The right side 夬 supplies the sound. The meaning later extended from 'pleased' to 'quick, fast', the dominant modern sense.