Tang Yichen, although pretended to be a cool and calm man all day long, but the man trusted a few people.
Even his own Secretary wasn't allowed to know more, which is why Lucy was informed about the whole concept very precisely. It could be said that the man did not need a secretary or an assistant, he preferred to walk all alone in his life, with the very few people he trusted. He was a cautious man or rather he has just guarded his heart pretty well.
But contrary to his personality, Mo Yuhan acted carefreely. Though he looked cold and unapproachable, he allowed people to come closer. But the man carefully laid around a dark web around himself. The moment a person tried to cross the line, he will get trapped desperately. There was no going back on it.
Secretary Yu dealt with the matters rather well which is why Mo Yuhan trusted him to a certain level but the Secretary was smart enough to not take it for granted.