| "A fan? That's all?"
"Try throwing it. You never know."
–Yumi and Odd in X.A.N.A. Awakens, Part 2
She is given a second one in the second season by Jeremie, who had updated the supercomputer. This increases her skill range and ways to block lasers.
Yumi fights using two metallic Japanese war fans, also known as tessen. However, Yumi does not usually use real-world tessenjutsu, the martial art in which a closed tessen is used as a club, to fight. Instead, Yumi's fans are designed to be thrown like frisbees. Once airborne, the fans open fully and act like circular saw blades, slicing through their target and then returning to Yumi like a boomerang. However, the fans may injure her if she does not catch them properly. Despite being designed for mid-range fighting, Yumi may also use her fans at close-range by partially opening them and using them to slash at her opponent. The fans are also capable of blocking and reflecting laser fire.
In the first season, Yumi only had one fan. However, in Season 2, she acquired another, enhancing her ability to both attack and defend. Also, since Season 4, Yumi is able to make her fans disappear and reappear in her hands at will, eliminating the need to carry them on her person, and also eliminating the need to catch them after they are thrown.
An unusual weapon, the fans require a particular level of skill to use properly. In the episode A Fine Mess, when Odd and Yumi switch bodies, Odd has a difficult time battling Creepers using them, and needs a short lesson from Yumi in order to use them effectively.
In Franz Hopper, Yumi's fans are temporarily upgraded so that they fly longer and farther, and automatically lock onto and hone in on targets and strike at different angles; just like Odd's modified laser arrows. This upgrade came from X.A.N.A. where he sent a spectre to impersonate Franz Hopper to gain the team's trust and make them turn their backs on Jeremie. However, these upgrades and modifications were lost later in the episode.
Use in other Media
Yumi's fans resemble average tessen. In the original series, they have black or brown ribs and a white and pink floral design on their plates. While being used for combat, the plates glow pink.
While a spectre on Earth, the design of the fans change to a yellow and pink background with white flowers. Also, when thrown on Earth, the fans acquire a serrated edge, resembling a circular saw.
In Code Lyoko Evolution, the fans have black ribs and white plates with a pink and purple striped design on them. They also glow white instead of pink when in use.
- Every member of the Lyoko Warriors except for Jeremie and Laura for obvious reasons has used Yumi's fans at least once: Aelita in Attack of the Zombies, Odd (in Yumi's body) in A Fine Mess, William in Lab Rat, and Ulrich in Hard Luck.
- Certain types of real-world tessen are thrown like Yumi's fans, although these tessen do not fold and have spiked ribs, and thus do not resemble the ones Yumi uses.
- Throughout the original series, the ribs of Yumi's fans intermittently change between black and dark brown for unknown reasons.
- Tessen are one of several types of Japanese war fans. Tessen were traditionally designed to look like harmless "cool one's self with a breeze" fans, rather than weaponizable fans. These were for situations where regular weapons couldn't be visible. Some swordsmanship schools trained students in Tessen use. The tessen was also used for fending off knives and darts, as a throwing weapon, and as an aid in swimming.
- Tessen fans are one of several kinds of Japanese war fans. Other types include Gunsen "軍扇", which were intended to actually cool the user. Additionally, there are Gunbai Uchiwa "軍配団扇" and Uchiwa Shumokuzame "団扇撞木鮫".
- The kanji for Tessen are "鉄扇", and the hiragana are "てっせん".