Here is the full list of all 43 Leveling up girls in another world achievements.
Encounter Tomoya at Moon Village
Let Ayumi convince you to train three times
Wake up after your first night in Aporia
Complete your first sidequest
Get your first skillupgrade
Don't let Fubuki manage your money.
Clear your first dungeon
It's been five years, welcome back
Learn about the girl's prickles.
Find Ayumi after she ran off
Find out about the true inention of Benedict and his gang
Meet an old "friend" with a bunny tail and ears
Encounter Iori, the Elven Archer
Encounter Hitomi in the castle
Every Adventure needs a break!
Meet Sachi for the first time... uuuh the most deadly assassin.
How to tame an assassin
Let Sachi hold your body weight.
Isn't it dangerous to feed an assassin?
Meet Hitomi again.
Find Ayumi standing in front of you, wearing a ... school uniform?
You didn't sleep for two months, did you?
Speed up your recovery.
Learn about Mikako's strength
Meet Isabelle's familiars
That's a weird way of demanding payback.
Let Tomoya use Sachi as her doll
Find Iori bathing in the river
Watch Tomoya fall for a classic slime trap
Find a strange girl manifest from the lamp.
Think twice, before you say "I wish"
And she's a demon princess?
Not a real threat, is she?
And she calls herself a demonprincess?
Get everything to make the potion
Does a fair maiden's kiss work?
Is she really defeated?
Is this the Happy Ever After?
Spend 100.000 Gold in the shop
Spend 1.000.000 Gold in the shop
Spend 10.000.000 Gold in the shop
Max out a skill for a girl
Complete ten different quests from the board