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