@KN-XIII not sure if you're still curious, but I'd assume it doesn't go much further, if it does at all. There were only 36 chapters of this. The anime might have been long enough to cover all of that since it had 24 episodes, and that might even be why nobody finished working on this. The Tick! Tack! - Never Say Goodbye is a side story here, but is listed as a sequel on MAL, so I suppose that might be something not covered in the adaptation, and all of its chapters are here.
@Glomoro
Thank you, it's still good to know.
I dunno if I'll have the guts to rewatch it again, I remember it as a rather slow pace anime (I was kinda seeking for romance anime at that time).
I also asked that as usually, the manga does have a bit more story compared to the anime (exception made for a long run anime).
If it's essentially the same, then no need to read it I guess unless there's some change?