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