The War

 Warning for mentions of violence and suicide.  TL;DR: A non-literal war that took place when Eichi Tenshouin restructured the unit system of the academy, gaining power through naming and villainizing the Five Oddballs, who were talented prodigies, and defeating them in lives. Any deaths that occurred were due to suicide, and only one is canonically confirmed.

Intro
“The War” is a period of time that occurred during the year before the current year in the Ensemble Stars! timeline, when reconstruction of the academy’s structure took place. While metaphors are often made about the war referring to it in violent terms, no literal blood was spilled during this process aside from bullying and/or suicide. After its events, a cenotaph was built to remember them.

While the war has several components, it can be broken down into the state of the academy during the last year and the efforts Eichi Tenshouin made to reform it.

While Yumenosaki Academy was lauded as a great school, known for churning out idols who would be successful in their careers, many of the attending students were lazy and had little motivation to participate in their activities. Units had no limit in regards to the members they could handle, leading them to often have inflated membership in which not all of the members participated. The student council at this time also had very little power, and was thought of as an insignificant group. Its president at the time was Rei Sakuma.

Eichi’s intention was to reform the school, stating that he would “remove every little bit of pus and filth, and wash Yumenosaki Academy clean”. He used Keito Hasumi, his childhood friend, who was part of the student council at the time, to execute these plans as well.

One of Eichi’s tactics was to single out specific students seen as geniuses, but also eccentric, as a group that could be villainized and then fought against so that his unit, fine, could gain prestige and power while tying them down. These were the Five Oddballs. While Eichi had decided on three of the members (Rei, Wataru, and Kanata), the last two (Shu and Natsume) were suggested by Tsumugi Aoba when Eichi asked him for advice. Eichi then weaponized fine to take them down one by one, and because they usually worked alone or with few others, had the numbers to work against them.

Most of the files and records that were kept regarding the events and units of the previous year have been destroyed by Tsumugi as shown in Pleiades Night. As such, many of the first years are somewhat ignorant to what happened, especially if their seniors hide their own involvement from them.

Chess
Reminiscence: Checkmate Chess was the precursor unit to Knights, and was at the time a disorganized unit with a large amount of members who enjoyed the privileges of a “veteran unit” without actually doing work. Its name changed semi-frequently, and seemed to be voted upon rather than decided by a leader. Before Chess, it was known as Backgammon. Leo Tsukinaga served as the songwriter, who would make songs for the unit’s members because he loved them all and believed they loved him back, despite their tendency to not show up.

With Eichi’s unit system in place, it became less rewarding to have so many members in one unit, so Chess split up into several pieces as members defected, often naming their units after chess pieces. Since “Knight” was taken, Izumi Sena registered the name of his section of the unit with Leo “Knights” after the latter suggested making the name plural.

Known members: · Leo Tsukinaga · Izumi Sena · Arashi Narukami

RYUSEITAI
Reminiscence: Meteor Impact, but info also given in Rainbow A long-lived veteran unit that existed even when Jin Sagami was a student. Last year, while still emulating heroes, they did not often resemble them, merely causing chaos and gaining a bad reputation due to this. When their captain and vice-captain were absent, they rarely gathered.

Known members: · Madara Mikejima (Purple, vice-captain) · Chiaki Morisawa (Color unknown)

fine
Reminiscence: Element fine was the prime instigator of the war; many of the occurrences during the year were due to Eichi’s planning and sometimes Tsumugi’s execution. Tsumugi acted as its leader and public face, having also gathered its members (Eichi aside). After Wataru's execution live, its members split up according to the contract that bound them together.

Known members: · Tsumugi Aoba (Leader) · Eichi Tenshouin · Hiyori Tomoe · Nagisa Ran

Valkyrie
Reminiscence: Reminiscence ＊ Marionette Functioned similarly to the way it does in the current year. As one of the Oddballs, Shu Itsuki was one of the people Eichi was trying to defeat, and did so by orchestrating a scenario where the lights went out during a Valkyrie live, revealing the fact that they had been lip-synching and ruining the perfection that Shu insisted on for all their lives. He “broke” after this, ceasing live activities.

Members: · Shu Itsuki (Leader) · Nazuna Nito · Mika Kagehira

DEADMANZ
Reminiscence: Crossroad A unit that performed at the underground live house for a night after Rei returned from overseas for the purpose of orchestrating a King's Game-type of live to chase the delinquents from the live house. In the week before, Keito and Koga had been practicing together, and Kuro made their unit costumes. Keito was the one who named the unit. While Kuro is not officially part of the unit, he performed alongside them.

Members: · Rei Sakuma · Keito Hasumi · Koga Oogami

Kanata Shinkai
An Oddball fought by AKATSUKI during the War. During this time, he was still known as a living God who granted wishes to others. Keito’s efforts to dismantle the belief of his godhood led Kanata to lose his following in the school, which led to a drop in his reputation. His “execution”, done by Keito’s AKATSUKI, was intentionally less brutal than Eichi’s methods and ended with Kanata and Chiaki performing together against them. Kanata ended up joining RYUSEITAI after this.

Wataru Hibiki
The last Oddball that was fought during the War. He was assisted by Hokuto Hidaka, who wore a mask and hid his identity during the live (he was known as “Hockey Mask” on-stage) due to the necessity to have 2 or more members performing at once. Wataru’s unit during the live was known as “Thirteenth Day”.

Rei Sakuma
Rei was mostly physically absent during the events of the War, having been overseas both to try and find a cure for Ritsu's weak constitution and having been sent away by Eichi, who wanted him out of the way due to his strong influence. When he was abroad later on, he was working on fixing problems in Yumenosaki Academy’s overseas sister schools, where it is implied that Eichi had stirred up trouble. When he returned, he was weakened and unfit to fight, so it is unknown if he had a specific execution live.

Shu Itsuki
See 

Natsume Sakasaki
Added on to the 5 Oddballs after the other four due to Eichi wanting there to be five and needing another member, as seen in Element. Nagisa Ran alludes to this in Wonder Game, referring to him as “the one added on just to reach the number needed”. A first year at the time, he was defended from much of the fuss by the others, who were all second years, and thus sustains no metaphorical “wounds” from the war compared to them. Perhaps because of this, he feels more distant from the rest of them, and is more spiteful towards those who hurt them.