Problem with Yui Toshiki mangas is that he could easily have made most of them hentai instead of borderline, I don't think you can really say any of his manga can be called NTR as no one is ever stolen, if they cheat is just for sex and at the end it's all good again, it's a shame that he fucked up Boku no Futatsu no Tsubasa as it's pretty much his only manga maybe worth reading, until you get at the ending that was pretty stupid, guess it could have been worse though...
About Hen, after reading all those spoilers I remember I atually had a look at all chapters, but didn't read because everyone said it was bad, strange how it lasted 8 volumes and have a prequel, Hen: Suzuki & Satou, that is 13 volumes, I think he's not good at long series, just look at Gantz, overral first half of both mangas are good, but more or less after starting the second half the story starts to get worse, Hen because of all those new characters and one of the mcs disapearing, and Gantz because it get stuck in one arc with a battle that is more than 30 chapters and felt like it would never end, and the aliens getting even more bullshit powers, althought Gantz ending was definitely better than Hen, it could have been a lot better, it was pretty Gainaxish and didn't even had a epilogue, I won't be surprised if Inu Yashiki starts to become bad after some time.