Yu Guolai was directly sent to the military camp, while Yu Zian changed his son's teacher, bringing new ones from a foreign country. They were a bit more strict. So Yu Weimin had to pretend to be a normal student. This was also in line with what had happened in the storyline as well.
At the same time, he also knew that his father was going to die soon. Still, he didn't want to change the storyline too much this time. So, as the war dragged on for months, Yu Weimin let his father go and joined the military.
A few more months passed after this, when the news of Yu Zian's being killed in action while bringing glory to the Yu Kingdom spread throughout the place. Everyone in the entire country was mournful.