So very good. The title, itself, is a hook. Getting into it, the character development is excellent. Main character is very relatable in his desire to please his girlfriend twins. Any considerate man would have the same mental gymnastics after finding out he's been duped by twins who both love him.
Seriously, this should be made into an anime. Just with the content of the first 130 chapters, there's enough content to fill out a whole first season. And, of course, there's always the question of "How will he deal with things now?" with every new development and revelation.
Excellent book. Only downside is that the individual chapters are too short for my taste. I prefer 1 chapter per scene rather than DBZ style 5 episodes for one part of one interaction.