I'm not sure how it's immature to react like that? I'm a huge fan of Mika-Sensei's works because they aren't your everyday cliché'd lovestory and instead have interesting stories and really well-developed characters (even though they obviously are sometimes very messed up) but there is exactly one thing that triggers a reflex to puke in me, and that's the look of amputees. I made it through the first ~40 pages until it was clear that Toma's arms were really cut off, but after that I just couldn’t keep reading. Which is sad, because judging by the comments the story seems to be really interesting. But amputees? No. My phobia of that is way too strong.
Just saying - it's not immature to stop reading if there's anything in it that makes you feel bad.
This is one of my favourites. It may not be incredibly 'romantic' and 'sweet', but it's a very unusual and darkly intriguing story you're unlikely to find very often. And also Toma really is beautiful and somehow alluring, his personality not weak and all "save me! save me!" like so many stereotypical uke's out there who HAVE ARMS to protects themselves with, unlike Toma. The relationship is disturbing but highly interesting. I love everything about this manga and for those of you who aren't immature and say "eewie~" at the first sight of anything you aren't fond of, I highly - HIGHLY - recommend this. <3