Don't like this ending to be honest, it feels like a happy ending for the sake of a happy ending. I don't even think it's that happy either. Yui desperately wants to go back living as girl, can't adjust well to having to pretend to be male, her beloved but broken family is fixed by another person and she never gets to experience that warmth she always craved, misses eight years of her youth being unable to live as girl among other things. So what's the author gonna do, resolve it organically and let us see her find the answer to her problems? No, contrive a life-or-death scenario for her beloved Yuuta and somehow the only way for her to save his life is to suck it up and continue eating shit for the rest of her life.
This manga had me hooked because it depicted an unpleasant side of genderswap and I was interested to see how the author intended to resolve it. To see it sweep all of those problems under a rug and basically say 'it's OK because she loves Yuuta' is disappointing to say the least.
I didn't like that webcomic ending but even that felt like a more natural course of events if we were to follow Yui's unresolved problem to its logical conclusion. Honestly, who would be surprised at her eventually committing suicide having to live like that and never making peace with her inner turmoil?