Pleasant, Happy
noun, な adjective
A pleasant pleasant person is super pleasant! They're happy and nice to everybody all the time!
ゆかい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
昔、「僕は殺しが愉快でたまらない」と言った少年殺人犯がいました。
A long time ago, a young murderer said, "I can’t help but find murder pleasant."