Karashina is a character from the anime Baku Tech! Bakugan. He is a Darkus attribute brawler whose partner Bakugan is Borg Mahisas, a creature resembling a deadly scorpion. Karashina is the leader and spokesman of a ninja trio known as the Shadow Sanjushi, a role that sees him acting as the primary strategist and voice for the group.

His appearance is distinct and somewhat androgynous, characterized by long purple hair and dark blue eyes. He wears a skintight black suit with red lining, which is accented by a yellow scarf featuring a red floral design. Over this, he sports a purple skirt and red-lined black samurai tassets. He completes his outfit with purple leggings and black shoes with yellow lining. His most notable accessory is a red forehead band inscribed with the character for Jyou, which signifies his loyalty and service to his master, Master Jyou.

In terms of personality, Karashina presents himself as a composed and calculating individual, fitting for the leader of the Shadow Sanjushi. He is highly devoted to his master and his comrades, Tohga and Jinza, and his actions are primarily driven by a desire to serve their goals. A significant part of his character is his motivation for vengeance, as he and his trio seek to avenge their master, Master Jyou, against his rival, Master Shimo.

Karashina's role in the story is that of an antagonist and a rival to the main characters, including Harubaru. He and his fellow Shadow Sanjushi initially appear as formidable opponents. In one of his early appearances, he observes a brawl between his comrade Tohga and Harubaru, ultimately calling off the match when he deems it hopeless for Harubaru, though Harubaru insists on continuing. Later, he and his team face Harubaru, Raichi, and Tatsuma in a significant tag-team brawl. Despite using their powerful techniques, the Shadow Sanjushi are defeated, and Karashina formally surrenders on behalf of his team. In a moment of character growth, he shares a handshake with Harubaru afterward, indicating a shift from bitter rivalry to a more friendly respect, with Harubaru suggesting a more amicable battle next time they meet. The Shadow Sanjushi also later appear as guardians of a Subterra Monolith, where they are defeated by the antagonist Zakuro.

Key relationships define much of his character. His bond with Master Jyou is the central motivating force for the Shadow Sanjushi. He works in perfect sync with his fellow ninjas, Tohga and Jinza, often combining their Bakugan into a formidable defensive formation known as the Infernal Fortress or Infernal Formation. Karashina also has a notable, though indirect, relationship with the protagonist Harubaru, who proves to be uniquely immune to Karashina's signature psychological warfare techniques.

Karashina is known for using two unusual ninja techniques that rely on psychological manipulation rather than direct combat. The first is the Poisonous Insult technique, which involves him reciting an opponent's embarrassing secret, causing them to lose focus. In the anime, it is shown that he has a minuscule autocue written on his index finger to help him remember these secrets. He has used this technique against Tatsuma, Hono Moetaro, and Harubaru, though Harubaru's short-term memory issues ironically make him immune to the insult. The second is the Soothing Waterfall technique, where he retells the sad backstory of Master Jyou to demoralize the opposing team, a performance he accompanies with very badly-drawn sketches in the anime. Harubaru is also shown to be unaffected by this technique. The name Karashina itself translates to mustard in Japanese.