Wishing to complete the Necromancer class change ritual in just three days was indeed a bit difficult for Misumi Mikoto, especially since Yu Chen himself had spent a full week preparing back in his time. Thus, he was indeed intentionally making things hard for her.
But Yu Chen had no one to guide him back then; he was self-taught, and he had to prepare all the materials from scratch, which naturally took more time. Now he had provided Misumi Mikoto with all the materials and was giving her on-site technical guidance, which was a much better condition than what he had initially.
Although three days was somewhat tight, as long as Misumi Mikoto was diligent, meticulous, asked questions in time, and didn't waste time, it was still possible for her to complete the class change ritual.
Of course, at the moment, Misumi Mikoto had no time to contemplate whether Yu Chen was being hard on her; her entire focus was on how to complete the ritual.