Honestly, I think that the harem tag is used way too hastily. It should be used when there is an actual harem rather than when just many girls like the MC.
@Readragmon Think about it, even unintentionally, Oni can awake their blood and go on rampages. It makes sense for the Momotarou to want to snuff out the potential disaster (whether that's moral or not is a different story).