Responses
Just as the author said: Is it wrong to feel lonely? Is it wrong to male mistakes?
No it isn't. As long as you're honest and try to find a better way.
beta
Reading the comments I was scared of the whole 'sleeping with other people' situation, but it wasn't that awful to see. I like that the author barely showed it and didn't picture them enjoying or 'feeling it' at all. It was merely out of loneliness and no romance or desire involved. If it weren't like that I would have been annoyed because the feelings of Junpei and Ei would have been tainted.
I also liked that they acknowledged their mistake at talked about it.
A nice read.