Well, about the art assets... A bunch of them come from their previous game, Lyndaria: Lust Adventure. Shana is an NPC in that game and theres sex scenes with the solo demon and demon brothers, playing the exact same animations.
The smaller animations that play during battle (after taunting) are brand new, but it's definitely not like all the sexual content in here was actually created for this game, which is disappointing. A shame since the art is good and it seems like we all love her design.
And yes, asset reuse in videogames is a good thing, but that's meant for things like props, environments and buildings e.t.c, not sex scenes...