Episode 1

Worst One I is the first episode of the Rakudai Kishi no Eiyuutan anime. It aired on October 3, 2015.

Summary
Ikki Kurogane, a teenager who is known as the Worst One throughout his school for his lack of talent, prepares himself for usual morning training. Elsewhere, Stella Vermillion, the princess of the Vermillion Kingdom is seen arriving in Japan and will enroll in the Hagun Academy. Upon finishing his training, Ikki returns to his room and walks in on a half naked Stella who was changing as the situation was made worst due to Ikki's bad attempt of getting even by stripping himself.

Ikki was then summoned to the director's office where he was criticized by Kurono for his indecent behavior before summoning Stella into her office for Ikki to formally apologize to her. Stella, however, demands Ikki to perform harakiri as an apology much to Ikki's dismay who accidentally blurted out that he refuses to commit suicide just over seeing Stella in her underwear. Enraged over Ikki's comment, Stella starts to emit flames with Kurono leaving the office to avoid getting involved. Ikki in desperation, claims that he was mesmerized by Stella's beauty, surprising the girl as her flames weaken out of shyness. As Ikki tries to explain the situation again, Kurono comes back and reveal that both Ikki and Stella are roommates much to their surprise.

Kurono then brings the two of them to their room and reveals the reasoning to why they are roommates much to Stella's displeasure as she gives more impossible demands to Ikki. To solve the problem, Kurono gives both of them the option of settling the issue with a duel which eventually escalated into a duel with the loser becoming the winner's slave for life under Stella's demand after Ikki's casual remark on the victor being unknown till they actually fight.

Stella is later seen preparing for her match with Ikki as she reminiscences her efforts to master her powers and is displeased with how others view her as someone with talent solely. Meanwhile at the battle arena, Ikki is seen conversing with Kurono on the terms of his graduation, win the Seven Stars Sword Art Festival. Stella then arrives at the arena and their match officially begins with both sides materializing their respective Devices.

Stella starts the duel by attacking aggressively but was continuously countered by Ikki who countered back after copying Stella's sword techniques, almost landing an attack on Stella but was blocked due to the difference in magic. Stella while lamenting on winning on her undesired way, activates one of her strongest attack Katharterio Salamandra out of respect towards Ikki. Ikki willingly admits that he lacks the ability as a Mage Knight, and reveals his trump card, Ittou Shura which that forcefully removes all of Ikki's physical limits, drastically increasing his powers. Dodging all of Stella's attack, Ikki successfully lands an attack on Stella winning the duel before collapsing due to exhaustion.

Stella is then seen in the hospital room, being taken care of, and Kurono comes to her room. Stella question Kurono on how Ikki could be an F-rank knight, to which Kurono explains that the system is based on the blazer's ability not the actual fighting ability. Stella asks Kurono how Ikki failed and Kurono explains that it was a complicated situation. Kurono then recommends to Stella to follow Ikki's footsteps as he is someone who works hard as well.

Stella then enters her room to find Ikki sleep on one of the beds. Stella gets on top of Ikki and begins to feel him, becoming shocked at her first touch of a man, Stella then hits her head after Ikki wakes to find what she was doing with him. Stella then talks with Ikki and apologizes for labeling him, when she didn't really know him. Ikki, smiles, and reminds Stella of her servitude to him. Ikki, then, orders Stella to be his roommate. Stella agrees and they both bump each others fist, promising on making their arrangement work.

Light Novel and Anime Differences

 * Kurono reveals Ikki and Stella are roommates in her office instead of their room.
 * Stella wakes up in a medical facility room in the anime instead of her own room.
 * Kurono did not reveal the circumstances surrounding Ikki and his family.
 * Nene, Touka, Ayase and Kagami was not present in the Light Novel during the mock battle between Ikki and Stella.