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