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