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