Tomoe Mikagura is the main female protagonist in the pilot OVA *Tailenders*. A genius scientist, she created the experimental "Tomoe Drive" engine. Following a serious racing accident involving racer Shiro Tomoe, she implants this engine to replace his damaged heart, saving his life but altering his physiology.

The Tomoe Drive links his heartbeat directly to his racing performance, making his survival and competitive ability dependent on the engine. Consequently, race regulations reclassify Shiro Tomoe as a mechanical vehicle component, barring him from racing as a human participant.

Tomoe Mikagura's specific motivations for developing the engine and performing the surgery are not detailed. Her actions, however, reflect a commitment to advancing scientific boundaries and critically influence Shiro Tomoe's quest to surpass legendary racer Loser King's century-old records. Her involvement remains central to the conflict over his racing eligibility.