Here is the full list of all 69 DEEP SPACE WAIFU achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Beat the PLAGUE boss
REMI naked
60% of clothes off REMI
30% of clothes off REMI
Unlock REMI TACHIBANA
NEKOTINE naked
60% of clothes off NEKOTINE
30% of clothes off NEKOTINE
MISAKO naked
60% of clothes off MISAKO
30% of clothes off MISAKO
Unlock NEKOTINE
Play with all the girls
NIKITA naked
60% of clothes off NIKITA
30% of clothes off NIKITA
Beat the ARMORY boss
ARISA naked
60% of clothes off ARISA
30% of clothes off ARISA
Unlock ARISA MIKEA
Gain 18 stars
YUMI naked
60% of clothes off YUMI
30% of clothes off YUMI
Unlock MISAKO AOYAMA
SARAH naked
60% of clothes off SARAH
30% of clothes off SARAH
Unlock NIKITA DORMER
Unlock YUMI MATSUDA
Beat the VULCAN boss
60% of clothes off MITSUMI
30% of clothes off MITSUMI
Unlock MITSUMI KATAGIRI
Gain 5 stars in one girl
MOKOTO naked
60% of clothes off MOKOTO
30% of clothes off MOKOTO
Date with a girl
Beat the SAMURAI boss
60% of clothes off TOMOKO
30% of clothes off TOMOKO
Explode your first piece of clothes
Play the dating app
See the credits
TOMOKO naked
Play one hand mode with TOMOKO
Beat TOMOKO with one hand
Play one hand mode with SARAH
Beat SARAH with one hand
Play one hand mode with MOKOTO
Beat MOKOTO with one hand
MITSUMI naked
Play one hand mode with MITSUMI
Beat MITSUMI with one hand
Play one hand mode with NIKITA
Beat NIKITA with one hand
Play one hand mode with YUMI
Play one hand mode with MISAKO
Beat YUMI with one hand
Beat MISAKO with one hand
Play one hand mode with ARISA
Beat ARISA with one hand
Play one hand mode with NEKOTINE
Beat NEKOTINE with one hand
Play one hand mode with REMI
Beat REMI with one hand
Unlock one hand mode