Tamashī Yūgō

With the goal to further improve the twins' genetic structure and give them additional abilities, the Vanguard of the Seven Swordsmen of the Mist infused in their DNA an unnamed Kekkei Genkai which will allow them to break down their bodies to its molecular level, giving them the ability to share each others' bodies as well as merge with others to destroy the host's cells from the inside.

However, instead of getting the expected results, the twins showed a different outcome: they become one whole new being whenever they merge. Codenamed Gurē (グレー, gray) by her creator and the twins, as a sort of pun on the girls' names, this new being appears as a woman in her early twenties, sporting an asymmetrical haircut, piercings and several black seals on her arms, body and legs. She possesses the Ketsuryūgan in both eyes, a trait that combines the individual eyes of the twins.

When it comes to her capabilities, Gurē is stronger, faster and more durable than the twins when they are separated. She can utilize the base Kekkei Genkai, allowing extra arms and legs to sprout from her flesh to deliver harder blows and confuse the enemy. It is also noted that in this form, the twins' other in-born and infused Kekkei Genkai are drastically bolstered.

From Misumi's observation, this new variation of the Kekkei Genkai is still evolving and theorized that there was still more that the twins will show her in due time. Until then, she continues to keep a watchful eye over the two girls, constantly inputting new data whenever they show progress.

Trivia

 * Overall concept of this Kekkei Genkai is a collaboration between Miyuu and Yomi.