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