I think I know where you went wrong - source, someone who did the exact same thing:
*SPOILERS - light ones, anyway*
- If you're lovers with Tocchan and keep visiting him at the agency while he's there, you'll get a number of scenes. The last one, I think, is where he decides whether to stay or go. So if you restore a few weeks back from the end and visit him like a fiend, you'll probably get a happier ending, or at least I did. As far as I can tell, you only need the full love meter for the last scene. I suspect whatever variable controls the good end is set to by default, so even if you never get the conversation, it treats it like you chose the wrong choice.
*END OF SPOILERS*
- As a side note, making the thing that controls the type of ending you get easily missable by people who just do dates or don't realize that you keep getting different scenes if you visit them in town is probably a first for me! Threw me for a loop, but I kind of like it... I'm romancing Shuu now (and god, so adorable), and it's made me basically stalk him around town like the obsessed lunatic I am. I've seen some funny stuff that I would have otherwise totally missed. :)