Comprehensive Comics: Invincible Starting from the Gravekeeper

An ordinary boy will find his own way through time travel. The protagonist, Mr. Zhang, traveled through the gravekeeper one day and started his own time travel journey. I don't know how to write an introduction. The author is a newbie, so feel free to scold me. It's been a long time since the author last watched those anime, and now I don't dare to watch them again. I'm afraid the plot won't be good, so let's start with the Gravekeeper first. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.