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