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My decisions. And all the situations they brought about. To think I only realized you were right after reaching this final outcome...
Real Name: Nanami Ayaka Affiliation: General Student Council (President) The individual serving as the President of the General Student Council in the academy city of Kivotos. Before Sensei arrived, she held authority over the Sanctum Tower through the Shittim Chest, but at the start of the story, she has gone missing after transferring that authority to Sensei. Currently, she resides in the Shittim Chest as Arona, the system administrator and main OS. She acts as a secretary-like presence assisting Sensei. Despite Sensei's advice and persuasion, the President stubbornly pushed through her own wrong decisions, ultimately leading to a massive failure. The flashback ends with her realization that while Sensei might not remember the advice he gave her now that he has been invited as a club advisor and acting President, he would likely make the same choices in the same situations—finding a path to a different result (a new future) rather than the wrong outcome (the destination reached by the President's decisions). So far, every new future chosen by Sensei has been a "Happy Ending."
An Arona from another timeline residing in the Shittim Chest. Her appearance is an inverted version of Arona's; she maintains a relatively stiff way of speaking and, unlike the always-smiling Arona, has a nearly expressionless face. She has long hair instead of a bob, covers her right eye instead of her left, has her braid on the opposite side, and her ribbon rises in the opposite direction of her halo. The ribbon is also larger. Her original name was A.R.O.N.A., but during the story, Arona begins calling her Plana. Since then, the name A.R.O.N.A. is no longer used, and the name Plana is used preferentially.

... Calculation complete. Hypothesis confirmed.
Proof finished. Q.E.D. ...I see. I understand now.
I understand why Arona-senpai is... a being similar to, yet different from me, the OS system A.R.O.N.A. of the Shittim Chest.
You were here. That is why no one could find you.
............President.
Back to the present
Peaceful Kivotos.
Schale's office.
Documents scattered across the desk...
And Sensei, who worked through the night, sleeping with his head on his arms in front of the monitor.
The Shittim Chest turns on. Sensei! Good morning!
A passing memory of Arona.
Release Date 2026.08.19 / Last Updated 2026.08.19