
I hope the real Si-won will find his happiness(╯°Д °)╯╧╧

Well it's not cliched really because mostly they just switch and switch back. If the theory was correct he would be stuck in his current body. If his body was still alive and they actually switched then it would become a bore since they would eventually switch back and the story will lose its meaning. That's just what I think :9

Being alive and switching back and forth is not cliched. Cliches actually work a little bit different than that. In either case having them both alive doesn't mean they both have to switch back and forth. In fact in order for them to both have happiness it would be necessary for them NOT to switch back and forth.
How i wish i know the author's other works, or it the only one ? So sad :(
Under the sheets is one of her works I think