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