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