You can enter Ash from the principal's office at school. After completing the third level event, a shop and the Waifu's house will become available, this is where the special sinners appear. To unlock the major event of the Third Act, you'll need to finish all interactions with her (both conversations and actions) and also buy all the special items from the shop. These items unlock gradually as you progress through the conversations.
Regarding the translation, it's definitely a challenge! I'm currently looking into machine translation solutions to provide at least a basic level of comfort for players.