Here is the full list of all 43 Leveling up girls in another world achievements.
Speed up your recovery.
You didn't sleep for two months, did you?
Find Ayumi standing in front of you, wearing a ... school uniform?
Max out a skill for a girl
Meet Hitomi again.
Isn't it dangerous to feed an assassin?
Let Sachi hold your body weight.
How to tame an assassin
Meet Sachi for the first time... uuuh the most deadly assassin.
Every Adventure needs a break!
Encounter Hitomi in the castle
Encounter Iori, the Elven Archer
Meet an old "friend" with a bunny tail and ears
Find out about the true inention of Benedict and his gang
Find Ayumi after she ran off
Learn about the girl's prickles.
Get your first skillupgrade
Wake up after your first night in Aporia
Encounter Tomoya at Moon Village
Don't let Fubuki manage your money.
Clear your first dungeon
It's been five years, welcome back
Let Ayumi convince you to train three times
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
Complete your first sidequest
Complete ten different quests from the board