With official chapters it's easier to see. It's where vol. 1 ends (ch. 122) and vol. 2 begins. The story doesn't actually seem to really have seasons, it's just devided in two parts that are kind of one season each. The first story is the one with mute guy and the second story is set many years in the future (don't wanna say who the second story's couple is cause that'll spoil too much)

Can any of you say where season 1ends?