Amnesia.

After having their lunch in silence, Gu Huan and Si Ban, both sat on the sofa with their mind somewhere else. The silence was disturbed by someone's phone, which was Gu Huan, looking at the caller he sighed and said to Si Ban, "I need to receive this." and excused himself.

After coming at the end of the corridor he answered the call.

 "Grandpa." he greeted.

"You brat, where are you?"

"Grandpa, what's wrong you were coming today why haven't you arrived yet?" He changed the topic and choose not to answer his grandpa's question.

As expected the old man forgot his question and charged towards Gu Huan with his furious words.

"You remembered, what a surprise! You brat, I'm still stuck here, I won't be coming, and you didn't even call me and asked about my delay. Don't tell me you forgot about your old man?"

"Grandpa, for once can you be less dramatic, please. I'm sorry, I didn't ring you, because I didn't see the time and when I did, you call