Here is the full list of all 20 Blackjack of Strip achievements.
Unlock armor
Unlock a deck of cards with mystical girls
Unlock a deck of cards with nude girls
Strip the enemy 50 times in a multiplayer game
Unlock a standard deck of cards
Strip the enemy 25 times in a multiplayer game
Unlock Takashi
Unlock Mrs santa
Strip the enemy 5 times in a multiplayer game
Strip the enemy 10 times in a multiplayer game
Unlock Santa
Unlock Dragon
Strip the enemy 1 time in a multiplayer game
Unlock Yumi
Win in a single player game 10 times
Unlock Snow Maiden
Win in a single player game 5 times
Read the rules in Russian
Win in a single player game
Read the rules in English