Suddenly, one day...

Book Yoshihide:

- Madly obsessed with finishing the Hellscreen.

- Cannot paint based on imagination/words, instead has to visually SEE events so that he can paint them. Why that is, is likely to capture a true understanding of hell.

- Sacrifices his daughter (although unknowingly) in this pursuit thanks to the Lord of Horikawa. Also loves his daughter, but ultimately feels nothing towards her the moment he sees the completion of the Hellscreen. Kills himself in the end.

Rien:

- Only cares to fulfill what the Prescripts (Hermes) tell him (finishing both his Roland cosplay and the Concept Incinerator).

- Prefers picture books because he claims you cannot understand the true intent behind an authors work if you can't see it yourself. His perfectionism with completing things also shows here, as he never finished the books he read to Ryoshu.

- Sacrifices Ryoshu AND Araya (knowingly) to finish his project. I personally do not think Rien felt genuine affection for Ryoshu, but he is capable of feeling something. Also kills himself in the end. Oh yeah he also had already watched his actual daughter die before in the past and did nothing but watch.

While Ryoshu clearly has similarities as well (particularly in also sacrificing her daughter), she doesn't have a project she's obsessed with completing. Her obsession IS her daughter. Book Yoshihide showed this obsession as well, although their relationship was quite estranged (similar to the estrangement between Ryoshu/Araya when she left the HoS and had forgotten some things about her).

The main thing that distinguishes Rien and Ryoshu from Yoshihide is desire. Ryoshu has that (like Book Yoshihide), Rien does not (arguably, I'm sure he feels despair and even ignored the Prescript in the end in a tiny act of defiance)

All of this is to say Ryoshu is somewhat of a counterpart to book Yoshihide, but if anything she is the Hellscreen itself. I think that part is more obvious though.