I think you'd greatly enjoy Undertale, it's a great 4-5h game exploring the combat/pacifist side of RPGs.

Agree, Undertale is absolutely brilliant in that aspect. Especially the beginning (the part that is in the demo version). The mood changes after that, for the worse I thought. Things got a bit more silly/naive than I like. The ending is absolutely brilliant again, tough, in the same way (it is a reflection on game mechanics). It is not 4h because you'll want to retry some parts.