In retrospect, she might need to be a virgin or at least pretty pure for that scene, as there doesn't seem to be a horny variation in the gallery.
Just rechecked all treasure rooms, if you didn't get Fragment #4 before defeating Malch, it's gone, no more best ending.
Unless it's a super hidden secret somewhere, but I doubt that.
Has anyone started on a proper list of skills acquired by endings/optional paths btw?
Can't find anything searching the thread, so while I missed a few, here's what I found:
Goddess Shadowdance (Active combat skill): Get a good ending, doesn't need to be the best one.
On activation, teleport around, slashing enemies anime-style.
Over-mutate (Active skill): Go to Malcholler/Stone Face with a Flying Penis attached to you.
Attaches the penis to her crotch.
(Are there any special scenes with it btw?)
Milking (Active skill): Go to Malcholler/Stone Face while spraying milk, do his quest.
Milk 200ml of breastmilk into a magic bottle, Stone Face gives you more bottles when you run out and chat with him.
Stored milk can be consumed to regain full MP.
Admitted Desires (Active summoning? skill): Get defeated by Malcholler, might need to be the scene noman_ex asked about above.
Supposedly summons Hypnohoods, doesn't seem to work for me, might have some conditions I'm unaware of.
Blue Sabre (Passive): Find in the Capra Prison, right most cell.
Deflect enemy attacks and stun them with the right timing.
Remnants of the Fallen (Passive): Get the Succubus ending by getting re-caught by a goatman after escaping the prison in shackles.
Doubles damage of the basic ranged attack, with the Nemesis buff it one-shots most enemies.
Twin Soul Aria (Passive): After getting Blue Sabre and being freed of your chains by the Mage, go back to where the armored Capra captured you, find a thing, go back to mage, loose the optional boss fight.
Doubles casting speed.
Freedom of Bondage (Passive): Get defeated by Malcholler.
Struggle free from grabs almost instantly.
Nemesis buff (Passive)[unlisted]: Find both pieces of a stone tablet in Withered Ruin, one is near the entrance, burn a petrified tentacle, then crawl through the hole, the other is right by the spear.
Doubles all damage done.
Still missing four actives.
EDIT:
Only missing two more thanks to
lampuiho