Here is the full list of all 15 Boobserman achievements.
Unlock Yumiko
Unlock Mizuki
Detonate 200 bombs
Collect all the negative bonuses
Unlock Aki
Detonate 100 bombs
Get caught by the censor
Collect all the positive bonuses
Unlock Shizuko
Get caught in the explosion
Unlock Naomi
Complete the game
Detonate 1000 bombs
Complete the game without getting caught by the censor
Complete the game without blowing yourself up