I agree the ending could have been more believable. I really liked ryuichi, too. Though, it seemed the author was kind of confused about how to portray him. Evil one moment, then nice the next, then evil again, kind of confused me about where she was trying to take him. But other his moments of split personality disorder I loved him and it seemed like she just wanted to get rid of him. Maybe she was ready to end the story and he was the only factor she had no idea what to do with, but I have to say I hated that nice guy act he did at the end, like he wasn't acting as shuichi's rival all throughout the whole manga.
I disagree. From the start, we knew that Ryuichi is an unpredictable fruitcake. And, a genius as well. You could never tell what he was thinkin: did he really listen to what was said? Is he really a just a child with a hand puppet? Is it all an act? You never know, unlike Shuichi, who is all about honesty, so confusion worked in Ryuichi's favour. So, it makes sense that the unpredictable genius would play the villian and the saint all at once. He always said he liked Shuichi, and had his own crazy, unconventional ways of helping him.
It was funny and the plot was acceptable, but honestly, I didn't enjoy the end at all.
This whole thing of his rival giving up about his singer carrer was horrible.
I'm sorry if I ofended someone who really loved the end, but I hated it.