Although I've enjoyed the vast majority of genres in Japanese popular music over the decades, I've usually gravitated toward some of the more urban contemporary and/or mellower compositions. And when it comes to the two expressions of "urban contemporary" and "mellow", my mental files on the various composers and lyricists focus on two people: singer-composer Takao Kisugi and his sister lyricist Etsuko Kisugi. Now, the two of them have often created works for other singers separately but they have also come up with songs in collaboration, a number of them having become hits.
For this Creator entry, I'll be focusing on those collaborations (although I may cover them separately sometime in the future). However, I have to admit that being more focused on the melodic side of things, the balance will be more weighted on composer Takao since there is a whole lot more information written about him than there is on his sister, Etsuko. As for the elder Kisugi, she was born in Tokyo in 1948, and initially began her career as a magazine editor and freelance writer, but after providing lyrics to her younger brother's early works, she became a professional lyricist. And she is still wearing that other hat as a writer of short stories and essays.
Takao Kisugi was born in 1950, and in his early 20s, he and two others created a band called Because (named after the song by The Dave Clark Five) which toured through a number of musical cafes in Tokyo. Although he was also able to participate in the production of Yosui Inoue's（井上陽水）first album in 1972, "Danzetsu"（断絶...Extinction）, as the acoustic guitarist, Kisugi had to go through the usual paying of dues through demo tapes getting rejected while he was working part-time jobs for the next few years. Then, he finally got his big break with his 1976 debut single, "Asai Yume" （浅い夢）which both he and Etsuko worked on. (The information from this paragraph was found in J-Wiki, but the original source was an interview on a 1996 episode of a TV Asahi program by the name of "Music & Talk: Ano Kyoku, Kono Hito".
According to the J-Wiki article on Takao, his musical influences come from The Beatles and Gilbert O'Sullivan. The Beatles are, of course, legends, and O'Sullivan I know because of "Alone Again". When I listened to this song again, I just went "naruhodo...". There is quite the similarity between him and Takao.
As I said at the top, I think of "urban contemporary" and "mellow" when I think of the siblings Kisugi. And probably his most representative song with that description is "Goodbye Day" from 1981. It fits the two expressions to a T, and the man himself was considered to be a New Musician which meant that he occupied another different niche in that 70s-created genre alongside the more janglier Tatsuro Yamashita（山下達郎）and the slightly more whimsical Yumi Arai（荒井由実）.
Takao and Etsuko were also coming up with love songs for the aidoru in the early 1980s. Among them, Akina Nakamori（中森明菜）is always at the top. Her debut was a Kisugi collaboration, "Slow Motion" (1982) about the gradual emergence of love between two kids at the beach.
I'll finish things off here with another song that I have already profiled, "Sailor Fuku to Kikanjuu"（セーラー服と機関銃）, the 1981 song that was yet another debut for another ingenue, Hiroko Yakushimaru（薬師丸ひろ子）. Just getting through this article had me changing my feelings about the Kisugi siblings. It hasn't always been about the mellow and wonder of love with them. Their creations could also go to the opposite end of the spectrum in that they could express the dramatic and difficulties of the concept as well. "Sailor Fuku to Kikanjuu" would be one of the latter examples as Etsuko talks about two lovers hoping to be together again in the future but not being able to at present due to various obstacles in their path.
At this point, I don't really know of any current singer-songwriters who have that similar Kisugi-esque approach to their music, so in a way, that sepia-toned element that has often been used in Takao's music has gotten even more nostalgic as the decades have passed. But you can take a look at the rest of the Kisugi collection for both him and Etsuko in the Labels section.