The Characters are well written just like in Undertale. There is a fair square of humerous scenes and the story is interesting.
My only complain though, is that the choices are feeling weird. Sure some choices seem justified, but sometimes it's hard to tell what, or if the choices have done something. Sometimes it felt like my choices did nothing or didn't even matter, or just felt confusing.
For the bugs, I have encountered only one so far. Here goes the Spoiler-Warning for those who haven't played it yet. The bug that I encountered occured Somehow in the ending when Chara showed up and gave me all these choices. I picked Sans and that black-haired orphanage-child (who's name I forgot) and let the scenario play out. When the text of the black-haired boy appeared, I hit the "Back" Button and an Error occured. At least there was that grey Interface with an error Message. I am playing it on Android btw.