BioTakuto was first discussed about by Barry who explained that he heard about Takuto because he was fighting with a Darkrai. Later, Conway revealed that Takuto managed to get all his badges and get through the first and second fighting rounds with just Darkrai. It wasn't until he faced Ash that his Darkrai was defeated. Takuto defeated Ash and moved onto the Sinnoh League finals where his Darkrai defeated his opponent by itself once again. Takuto became the Sinnoh League Champion.
In the eight Gym matches leading up to the League, Darkrai was the only Pokémon Takuto used to battle against the gym leaders and was able to win all the matches. Takuto's Darkrai also managed to get through the first and second fighting rounds of the Sinnoh League all by itself. Satoshi's Sceptile finally managed to defeated it.
Takuto's Latios was sent out to battle Ash during the semi-final round of the Sinnoh League. Latios had never previously been sent out during any of Takuto's battles in the Sinnoh League or during his Sinnoh gym matches as his Darkrai had never been defeated until Satoshi's Sceptile defeated it. Ash's Pikachu faced Latios and the two ended up knocking each other out at the same time.