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