Yumi Ishiyama is a highly valued member of the Lyoko-Warriors. She is considered the maturest of the group, being a year older than the rest of them, and takes care of the younger members. She is both Ulrich's and William's romantic love interest, and Aelita's closest friend.
Yumi was born in Tokyo, Japan, although her family immigrated to France when she was just a baby. She's the greater daughter of Takeho and Akiko Ishiyama, has a lower brother, Hiroki, although it begins to earn more importance in the series from the second season. She's the highest of all Lyoko-Warriors. She's 15 years old since the episode "Lab Rat". Her hair is black and short, always wears black dresses and carries appearance to be a free and independent girl. It is very generous and kind. Expert in Martial Arts, practises Pencak Silat in the gym with Ulrich. She's very fast, and establishes a new record in the school in career of speed, in the class of physical education (although in reality she was concentrated in going to the Factory).
She is the only one of the group living off-campus, the others being dormitory residents. Socially, her relationships do not seem to preoccupy her much, she seems to pay real attention only to her inner group of friends. While some schoolmates admire her when others despise her, she pays no attention rather focusing her attention only on her group of friends. She is shown to be very popular among boys who are interested in her, enticed by her natural and cryptic beauty. Yumi, however, often kindly rejects any attempt on their part. Yumi is undoubtedly the most mature and the most thoughtful of the group. Naturally warranting respect, her opinion is always taken into account. She always acts within the group as defending others: it is she who makes important decisions on the group's direction, and it is to her that they come for advice.
- ID Card: The back of Yumi's card shows a kind of parterre flower.
- Health: 100 Life Points
- Tessen Fans - she has two Tessen Fans, lanced as Boomerangs, which also serve as a shield.
- Lyoko Powers/Abilities:
- Telekinesis - This power allows Yumi to remotely move objects, or even allies (Aelita in "The Attack of the Zombies"). It must therefore focus, and therefore can't attack with her fans (but she can use telekinesis to attack lifting objects and send them to the enemy). A purple halo surrounds her when she uses that capacity. Note that this power is the most versatile, and it fits perfectly with Aelita's Creativity. She also has Telekinetic blasts, Telekinetic shields and Telekinetic waves.
- Superhuman balance and durability - She's very good dodging shots with his agility giving jumps and doing wheels. Besides, she has very good balance, that uses to walk by horizontal bars very narrow.
- Vehicle: Overwing
In this alternate continuity based off of the pilot of the show, Yumi is a boarder much like the rest of the cast, and while still older than the majority of the group, is in the same grade as the other Xanadu Warriors due to being a year younger. While her general appearance is the same as in canon, there are many differences between this version of Yumi and her canon counterpart. Her personality is generally the same as it was before, except she is more determined to stop the disturbances in Xanadu.
Yumi moved from Japan to France when she was six years old, along with her younger brother Hiroki, who was only three at the time. Until transferring to Kadic, Yumi's life was not easy, as many in France were rather sore about the economic impact of Japanese businesses, causing a great deal of racism-related bullying to occur. While Yumi was able to fight it off, she reached her tipping point when Hiroki and his new friend Johnny were in the midst of a terrible assault that caused Yumi to breakdown into a protective rage. Yumi was sent to Kadic as a result.