Here is the full list of all 37 Gal*Gun 2 achievements.
Unlock all other achievements.
Call a girl over to your house for the first time.
Reach Risu's good ending.
Finish Nanako's route A.
Finish Nanako's route B.
Finish Chiru's route A.
Reach the Harem ending.
Give 50 girls euphoria with Lovestrikes.
Upgrade your Pheromone Goggles to their final form.
Get every girls' phone number.
Take a good look from below when you have a girl over.
Get kissed by 50 girls.
Get stepped on by 10 girls.
Get stepped on by 50 girls.
Have plenty of conversations with Chiru.
Have plenty of conversations with Nanako.
Reach the ending for the first time.
Finish Chiru's route B.
Give 30 girls Striphoria.
Clear all of the Kamizono Sisters' requests.
Upgrade your Demon Sweeper to its final form.
Get kissed by 10 girls.
Clear your first Doki Dokie Mode.
Suck up 500 mini-demons.
Clear your first search mission.
Give 500 girls euphoria.
Use the Demon Sweeper to give a girl Striphoria for the first time.
Clear your first defense mission.
Suck up 100 mini-demons.
Suck up a Metal Kurona for the first time.
Give a girl a snack for the first time.
Give 100 girls euphoria.
Get 50 ecstacy shots in a row.
Get 30 ecstacy shots in a row.
Clear your first regular mission.
Perform a Lovestrike for the first time.
Get an ecstacy shot for the first time.