They switched phones, so that their lie so that their lie wouldn't be discovered.
Yea but I was pointing out how the other girl was texting Xianfeng's phone with him,as a girl, right next to him but Yushuang was answering them in the daytime... Like wouldn't it make more sense if she was at their apartment as a boy since it was night time? or was it the day after? I just thought maybe the author got mixed up and forgot that if Xianfeng was a girl then Yushuang would be a boy...
Oh dang your right, yeah that's really weird! ༼⁰o⁰；༽
She has her period (she doesn't change when she's menstruating) as she stated when she went home. (⌒▽⌒)
If Xianfeng is currently a girl at a thing at night and that girl is texting his phone, how is Yushuang answering the texts during the day and as a girl...? that's a big thing for the author to miss...