yes, last year of mid school
If I am not wrong they mention that jian yi suddenly disappeared in the 2nd day of their high school in the earlier chapters (prolly around chapter 40s) so I am guessing they are already in high school?¿ And about their ages I am not entirely sure but I am guessing they 19.
jian yi second disappearance is not happening yet, it should be after they garduated mid school, from chapter 51 until now are all flashbacks on what's happening in the last year of mid school
Thank you for the clarification!
Somebody help a girl out, how old are they? If I'm not wrong they are in their last year of middle school right? Or are they actually in high school? Really confused......