Hayate no Gotoku! Chapter 175:You Bump Into Everyone You Need in Life (人生に必要な人とはだいたい出会うようにできている,Jinsei ni hitsuyōna hito to wa daitai deau yō ni dekite iru?)
In this chapter it is revealed how Chiharu met Sakuya and became her maid.
Before the start of the arcade game, Chiharu says to Sakuya "You won't die, because I'll protect you". This is a reference to the quote Rei Ayanami had used in episode 6 in Neon Genesis Evangelion.
As Chiharu and Sakuya leave, it is revealed that the name of the arcade is "Amusement Game Arashi". This is a reference to the series Game Center Arashi.