Akayu

Akayu is a bit beast who can dominate the playing field with speed, cunning, and formidable battle skills. It holds power over hellfire and is partnered with the Beyblader Kei Hiyomura.

History
Akayu is one of the fox spirits mentioned in Japanese myth. Instead of just luring people to their deaths, however, it was responsible for their demise as well, feeding on their life energy. A priest from the Fujiwara clan eventually managed to seal away the 'troublesome' spirit within a stone. The same clan member had the stone carved into a figurine that would later be handed down from generation to generation, given to a designated protector each time.

The partnership was a mutual one, where Akayu protected the clan and did the protector's bidding in exchange for its own growth in power and abilities, thanks to the souls it consumed. This earned it the name 'Sessho-yako' -  'killing field fox'.

The figurine was eventually given to Yumi Fujiwara who, though recognized as a possible partner, saw no reason to call on the fox at any time. Later, Yumi's husband Takeo Hiyomura ended up in the employ of Boris Balkov, who found out about the fox spirit. He had his scientists test their spirit extraction procedures on the figurine, succeeding in drawing Akayu out and modifying it before siphoning the power into a bit chip.

Beyblade
Akayu made its first appearance when Kei attempts to leave the Blade Sharks; Casey, Stuart, and Trevor challenge her to a Beybattle, saying that if she loses, she has to stay with the gang. Blader and bit beast easily overpower the trio, ending the match in seconds. It appears again, only partially, during one of Kei's matches in the regional qualifiers.

Beyblade V-Force
Around the same time the Saint Shields were making their way through Team Psykick's headquarters, Kei and Katou were doing the same with the help of their respective bit beasts, only in another part of the compound. When the pair's actions accidentally caused a collapse in one of the corridors, Akayu protected its partner and helped clear a way out. It later was used during a demonstration match, and in various tag-team tournament matches that Kei participated in.

Beyblade G-Revolution
Akayu doesn't appear until the middle of the series, when Kenny mentions his curiosity about how a match between Kai and Kei would turn out. The two agree to a practice match that the young researcher can record on his laptop, but the simple match soon becomes a full-out battle. Kei later has her bit beast help guage how strong the BEGA bladers are, although she and Akayu hold back so they don't attract Bori's attention.

Attacks
Akayu has several attacks, both physical and special, that change to suit the Beyblade Kei is currently using. As a reaper, it can use the fumes and flame it controls to create illusions as well.

Gogyou F

 * Explosion - Gogyou attacks from the opponent's flank
 * Ignea - Akayu quickly rains fireballs down over an area.
 * Flame Bomb - Gogyou moves around the dish, heading towards the center, and Akayu cloaks the blade with fire before it lands the final blow
 * Aura Blast - the movement is the opposite of Flame Bomb, with Gogyou moving towards the rim of the stadium before launching into the air and attacking the opponent from above.

Gogyou V

 * Strata Flare - Akayu cloaks the blade in flame as it moves away from the opponent; the blade then doubles back to strike
 * Flame Torrent - Gogyou rushes the opponent when it's on the slope and attacks from below, at the same time launching itself into the air. Akayu then fires a huge fireball at the destabilized bey.

Gogyou G

 * Ember Storm - this combines the spiral attack pattern of Flame Bomb and the final aerial attack from Flame Torrent, but takes less time to execute.
 * Burning Siege - Akayu creates a copy of the Beyblade to confuse and distract the opponent, with the real Beyblade attacking from behind and using a 'flower-petal' pattern to deal multiple hits
 * Flare Blitz - something of an upgraded version of Burning Seige, this time with more than one copy to serve as distraction

Gogyou MS

 * Inferno Rage - flames surround both Kei and Gogyou, with the latter circling the dish at high speed, visible only for a moment before it connects with the opposing Beyblade
 * Spirit Blaze - flames surround the Beyblade as it rushes down the slope, dealing multiple hits to the opponent before knocking it out of the stadium

Gogyou MF
Akayu also has several techniques it can execute regardless of Beyblade being used, namely:
 * Inferno Ruin - Similar to Flare Blitz, with multiple illusion-copies of Gogyou performing an aerial attack simultaneously, causing an explosion in the stadium
 * Hellfire Burst - Akayu creates several fireballs and sends them towards the opponent; once close enough, they combine and cause an explosion on impact
 * Magma Wall - Akayu creates a wall of flames that spread outward to blanket the stadium
 * Hades Sphere - Akayu generates several rings of flame to trap the oppponent, then generates illusions of itself that attack all at once
 * Oblivion Flare - Gogyou moves at high speed, creating the illusion that there are two of it in the dish, while Akayu creates a ring of flame that spirals outward, and another that just moves away from the Beyblade in the center, growing larger as it goes; once the opponent is trapped, Akayu moves in to strike, bringing the flames with it and knocking the opponent out of the dish with the force of the blast

Trivia

 * Akayu actually has two names. The first one comes from the words for 'red' and 'ghost', referencing its red color as well as its original form as a fox spirit that can reap souls. Kenny once remarked how this was the polar opposite of Dranzer, who is a phoenix and represents rebirth. Its true name - before becoming a bit beast, was simply Sekitsu or 'red fox', because of its fur staying red even after gaining a 9th tail.
 * Akayu assumes a little of its previous partner's personality, and since Yumi was its last partner, it treated Kei in a motherly fashion when they were first introduced.
 * Kei usually refers to Akayu as female, even though the fox spirit is inherently genderless.
 * Akayu has a dark version of itself that isn't separate from it, unlike other bit beasts with a dark version like Dragoon and Dark Dragoon. When asked, Kei explained it as Akayu being a fusion of both, with its ambiguously moral nature as the proof of this.
 * Akayu can use Kei as a conduit for its flames, making the latter immune to burns whenever in a Beybattle. This was also one of the ways it protected its partners before being enhanced by Biovolt.
 * It's possible that Akayu will change its appearance depending on the gender of its partner. It's also likely that the Beyblader subconsciously 'chooses' Akayu's appearance.
 * Akayu's history is based loosely on the tales of Tamamo-no-Mae and the Sessho-seki ('killing stone') that Tamamo-no-Mae's corpse became. The stone was said to release toxic gas that killed all life around it, tying in with Akayu (or Sekitsu) being a spirit reaper.