Greetings!
I'm a pretty big Anzen-Chitai and Yosui Inoue fan, so I can give a little info here.
I own one Anzen-Chitai "Best of" CD (Cat. # H32K 20110). This has twelve of their biggest hits, including "Wine-Red no kokoro", "Koi no yokan", "Suiksa", "Jirettai" and the duet with Yosui Inoue entitled "Natsu no owari no Harmony". I highly recommend this CD for anyone to check out the Anzen-Chitai sound.
Yosui Inoue has a 2-CD "Best of" collection entitled "Golden Best" (Cat. # FLCF-3761) which is pretty comprehensive. It includes many of his hits from the 1970's: "Kasa ga nai", "Kokoro mo you", "Yume no naka e", etc. and it also contains some of his more recent songs: "TEENAGER", "Tokyo", etc. You also get to hear his versions of songs he wrote for other artists, including "Wine-Red no kokoro" for Anzen-Chitai and "Asia no junshin" for Puffy.
I'd definitely agree that both of these artists are in the same style as Kazumasa Oda. I think Kyousuke Himuro is considerably more rock-oriented, so his sound has a harder edge. Masaharu Fukuyama really runs the gamut, so he has harder and softer hits.
I'd recommend the group Tulip if you like K. Oda, or the solo stuff from Tulip lead singer Kazuo Zaitsu... in fact, at one point Oda and Zaitsu sang together on a #1 single in Japan (a trio which also included Yumi Matsutoya). The Tulip song "Saboten no hana" served as the theme song to a popular drama series.
Hope this helps...