That's because it's not ch5 but ch6 and was misdesignated by the TLeruhhhhhhh... I think something was lost in between chapters 4 and 5, the chapter 4.5 seems to be a mix of light novel and a 4koma which references a character that hasn't even been introduced yet, and the start of chapter 5 seems to be skipping some things based on where we left off.