Crooned by actor/singer Masatoshi Nakamura（中村雅俊）, this song got a lot of high rotation at my old karaoke haunt of Kuri in Yorkville. And it's very much a nocturnal song...good for listening and drinking simultaneously....thus the Mood Kayo label. Written and composed by Southern All Stars lead vocal Keisuke Kuwata（桑田佳祐）, supposedly the lyrics are pretty racy and perhaps dripping with innuendo, but since I was never a lyrics man anyways, I've enjoyed it for the light bossa nova melody with a kayo twist. Released in September 1982, it went as high as No. 5 on the Oricon weeklies.
Another interesting point of trivia about "Koibito" is that it was used as a theme tune for no less than 2 separate TV dramas and a movie with none of them having any connection. Another hilarious point from J-Wiki is that the organization Advertising Council Japan (AC Japan) used the song for its campaign on child vaccinations. Considering the lyrics, I'm not sure if this song would've been my first choice on the battle to defeat whooping cough or tetanus.