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 REMI with one hand
Play one hand mode with REMI
Beat NEKOTINE with one hand
Beat ARISA with one hand
Play one hand mode with ARISA
Beat MISAKO with one hand
Play one hand mode with MISAKO
Beat NIKITA with one hand
Play one hand mode with NIKITA
Beat YUMI with one hand
Play one hand mode with YUMI
Beat MITSUMI with one hand
Play one hand mode with MITSUMI
MITSUMI naked
Beat MOKOTO with one hand
Play one hand mode with MOKOTO
Beat SARAH with one hand
Play one hand mode with SARAH
Beat TOMOKO with one hand
Play one hand mode with TOMOKO
See the credits
NEKOTINE naked
REMI naked
Beat the PLAGUE boss
60% of clothes off REMI
30% of clothes off REMI
Play with all the girls
Play one hand mode with NEKOTINE
Unlock one hand mode
30% of clothes off NEKOTINE
60% of clothes off NEKOTINE
ARISA naked
Unlock REMI TACHIBANA
60% of clothes off ARISA
30% of clothes off ARISA
Beat the ARMORY boss
MISAKO naked
60% of clothes off MISAKO
30% of clothes off MISAKO
Unlock NEKOTINE
NIKITA naked
60% of clothes off NIKITA
30% of clothes off NIKITA
Unlock ARISA MIKEA
YUMI naked
60% of clothes off YUMI
30% of clothes off YUMI
Gain 18 stars
60% of clothes off MITSUMI
30% of clothes off MITSUMI
MOKOTO naked
60% of clothes off MOKOTO
Unlock NIKITA DORMER
Unlock MISAKO AOYAMA
TOMOKO naked
Unlock YUMI MATSUDA
Beat the SAMURAI boss
30% of clothes off MOKOTO
Unlock MITSUMI KATAGIRI
Date with a girl
Beat the VULCAN boss
SARAH naked
60% of clothes off SARAH
30% of clothes off SARAH
Gain 5 stars in one girl
60% of clothes off TOMOKO
30% of clothes off TOMOKO
Explode your first piece of clothes
Play the dating app