why did Sai take the paper lily in the true ending?

[m]

i love aoi and sai but sai is too suspicious

[¤RAV¤ Jesus]

There is a good chance that the door that Lacie used isn't the only one of that type , and you would need a Paper Lily to open one , so there is a pretty good chance that it's because it's a useful item.

[All Hail Britannia!]

This is purely my guess, but it seems to me that Sai simply does not want to return to our world.

[Finitus]

i think sai may be stuck in the other world on purpose. maybe it has something to do with why kat went into the other world, or he could be avoiding something. i am excited to see more of both sai and aoi in the next chapter. hope leef manages to make chapter two as excellent as the first one!

[iaman2b]

You have to defeat Miss Knives and get the tower's doorknob fragments that Spider gave you to reach the true ending of chapter 1. If you return home without the doorknob fragments, that is the dead ending. As for Sai, he doesn’t have much influence on the plot of this chapter. He may just be holding the dungeon door for you.

[76561199500428015]

If he took the paper lily, he probably took the return doorknob too when he left the cursed door so he could go through any other cursed door. My guess is he went back through the facility but avoided the weird bunny thing and got to the door he had arrived through. Considering his face is on the Chapter 2 save file and not Lacie's, we'll most likely be figuring that out soon enough anyways. Also, I don't think he's actually suspicious because of the dead ends like Underwater Misadventures and What's At Stake- if his fate was ambiguous in those, I'd definitely be more wary of him.