The number 6 appears frequently in Japanese anime. What does this mean?

It may be related to tarot cards (such as the varieties in Tokyo-please refer to the plot analysis post), and 6 refers to lovers (6). Tarot cards can analyze, predict and provide suggestions for different needs such as love, interpersonal relationship and work (school). Especially when you don't know what to do, it is a very good road sign and has a certain psychological suggestion. Because it is too mysterious, it belongs to the category of mysticism. Some scholars use tarot cards for divination in psychological counseling, but generally only use the analytical function of tarot cards.

It may also refer to the six roads of hell (such as Rokudou mukuro's eyes in Family Education).