After middle school, Tsukasa went on to Eitoku Senior High with his friends, the F4. At some point, they took control over the school and stopped wearing the school uniform. They also began handing out red cards, a "declaration of war", to those who defied the F4, including Kimoto.
Tsukasa first met Tsukushi Makino, after her friend Makiko Endo fell down the stairs and landed on him. Tsukushi stepped in, when he refused to forgive Makiko. He transferred his ire to Tsukushi and gave her a red card. However, Tsukushi decided to fight and delivered her own red cards to the F4. Tsukasa did nothing at first, allowing the other students to bully Tsukushi. Determining that his honor was on the line, Tsukasa made his next move and hired four Eitoku students to assault Tsukushi. Rui Hanazawa, unbeknownst to Tsukasa, protected Tsukushi from the attack.
After the failed assault, Tsukushi kicked Tsukasa in the face in retaliation. The kick strongly reminded Tsukasa of his older sister, leading him to develop a crush on Tsukushi. Tsukasa subsequently kidnapped Tsukushi and brought her to his mansion. She was given a makeover from head-to-toe at his home salon. Tsukasa offered to allow Tsukushi to hang out with him, which she rejected by saying "I'm not for sale". Despite having his advances spurned, Tsukasa was still attracted to Tsukushi.
Tsukasa was first portrayed by the voice actor, Takumi Nishio in the three drama CDs. The creator of Boys Over Flowers, Yoko Kamio was happy with his performance and felt "he caught that slightly dopey drawl of Tsukasa's". Upon telling Nishio and Takuya Kimura (Rui Hanazawa's part) that they fit the character's images, Kimura jokingly told Nishio that Kamio said he was as stupid as Tsukasa.