Yuichi Masumi decides that he's interested in engaging in a relationship with Shiro Tobita, whom his friends consider strange. What they don't know is that, despite his poker face, Tobita has much to share with Masumi that he might not be ready for, because it's difficult to call it anything but a lesson (or three ... or thirty-three) In Kink 101.
Like how a single note in a really nice song might not be great by itself, but the singer manages to hit it just right in a live performance, this simple but somewhat morose story, with all of these, erm, not-very-fluffy themes (casual sex, bondage, hardcore puppy play, sadism etc)/plot movements/characterizations, just has this perfect balance of nice slice-of-life and tragic pathos. Symbols/motifs run the gamut from epic and celestial to deep and chthonian. As well, Ido Gihou takes a page out of older manga styles and uses them skilfully. Lastly, it's interesting that there are parallels between the cultural perspective that individual people can take on how to feel about being same-gender-attracted and about liking something outside of the sexual norm, aka. not liking 'vanilla' sex. This honestly isn't portrayed with any judgment, but there is a sense of close-mouthedness; you need to figure out whether the characters are rejecting each other or just having a think, and it's everything to you, as the reader, to finally know the truth.
Really, REALLY good if this kind of story rocks your boat. Meditative and beautiful to look at, even if it's not.