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.
Have plenty of conversations with Chiru.
Have plenty of conversations with Nanako.
Finish Nanako's route A.
Upgrade your Pheromone Goggles to their final form.
Finish Nanako's route B.
Reach Risu's good ending.
Upgrade your Demon Sweeper to its final form.
Get stepped on by 50 girls.
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.
Clear all of the Kamizono Sisters' requests.
Give 50 girls euphoria with Lovestrikes.
Get stepped on by 10 girls.
Suck up a Metal Kurona for the first time.
Reach the ending for the first time.
Finish Chiru's route A.
Give 30 girls Striphoria.
Give 500 girls euphoria.
Clear your first Doki Dokie Mode.
Use the Demon Sweeper to give a girl Striphoria for the first time.
Suck up 500 mini-demons.
Clear your first search mission.
Clear your first defense mission.
Suck up 100 mini-demons.
Give a girl a snack for the first time.
Give 100 girls euphoria.
Perform a Lovestrike 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.