Guide based on ULMF Nursery Slime thread: https://ulmf.org/threads/doubles-core-daburusu-koa-nursery-slime-bizarre-days-with-a-slime-girl-nursery-slime-suraimu-to-na-re195886-rj195886.10156/post-949494
Item/scene acquisition guide
Slime:
Scarecrow: unlocked by default.
Mirror: obtained by saving the grandma in town from the "mirror world" mini-dungeon in her house late into the game.
Succubus:
Flower: bought from the street vendor.
Magic Circle: Talk to an inn staff near the stairs at day, then talk to a strange woman next to the inn at night. Then enter inn 2f at day, and choose to deactivate the magic circle (miniboss).
Carbuncle:
Mimic: talk to a girl atop the bridge in town at day, then head to the "sewer cleaning" quest and check the sparkle near the top right of the map (miniboss).
Crystal: after fishing out the legendary (highest reward) fish in the fishing quest, talk to the shipcaptain in town at day. Return to the fishing quest and continue fishing at the rightmost fishing spot (miniboss). Return to the captain.
Queen Bee:
Spear: talk to a young man near the topleft of the adventurer's guild and accept his challenge (miniboss). Win.
Teddy Bear: talk to the young girl near the topleft of town. "Water" the plant in front of her with an Energy Ampule (revive item). Do it again the next day, then use a Super Ampule (better revive item) the next day. Talk to the girl.
Catgirl:
Cat: talk to the cat in town while Kuu is in Catgirl form. Find the cat in the town market, the "lost cat" quest, and your home, in that order.
Sword replica: talk to one of the men in the inn, who offers to make the item if given three items. One is sold by the street vendor, one is found in the "poison marsh" quest, and another is an uncommon drop from the invisible monsters.
Minotaur:
Wine: The drunkard in town at night. Talk to him, then talk to him again with a certain food item (IIRC, it was the one with +200 HP, +30 MP, +4 Luck). Give him the item.
Axe: One of the people in the guild will talk about an axe in the labyrinth. Head to the "icy labyrinth" quest, and find and interact with the axe (preferably with Kuu in Minotaur form). The path to the axe doesn't always show up, so you might need to run the quest a few times.
Wraith (Ghost):
Gravestone: Talk to the strange girl near the topleft of town at night while Kuu is in Wraith form. She will give you an item. Go to the "Tower" quest, and unlock the door midway through. Check the gravestone.
Demon gate: One of the people in the guild will talk about demonic possessions and how someone close to the possessed will likely be possessed too. Head to the "possessed girl" quest, and talk to the mother. Repeatedly. Over and over and over again. Eventually you get a miniboss and automatically finish the quest.
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Endings
Toris Route: Must have finished all of Toris' "talk events". Mostly, this can be achieved by simply talking to her every day, and taking your time overall. The final talk event should unlock after you've paid the per-day "rent money" enough times, giving you the Isis Coat (statistically the strongest armor for Oswald bar none).
Kuu Route: Must have unlocked all of Kuu's bedtime H-scenes, obtained by unlocking more doodads in the nearby garden. The list is as follows, and unlocks as you rise in rank.
Omake (restaurant/harem) route: must have finished the extra dungeon. Must have finished both the Kuu and Toris routes. Kuu must have eaten the Oswald Course (best craftable food item at the very bottom; HP+200, MP+40, all stats+10) at least once.