Yin and Yan were separated in the war until they reunited 10 years later. Their cruel destiny had placed hard choices between both. Not wanting to be betrayed again, Yin turns his sister Yan into a puppet in his control, stating that he will never leave her again.
Yin is a master puppeteer able to control his puppet sister Yan by summoning her. This can incapacitate his opponent. His strongest skill is to raise Yan's elemental stats in both offense and defense, and he can full restore a single HP with drain.
This form requires Kazusa in 3★ Mythic and 30 Puppet Augite Shards; the shards are obtained in the Augite Trial within the Augite System, and won at the Thrones of Paragon once randomly. It shows two scenes where Kazusa decides to aid Kurasame against the Black Shadow, but fails as Kazusa is ensnared by it. Wanting to save Kurasame from an incoming attack, Kazusa transforms into Yin by using Yan to protect him. Kurasame is surprised by Kazusa's second form. Once Yin is acquired, it shows a different scene where Kazusa is in his room full of technology and chemistry, and has a female puppet lying on the ground. Kazusa drinks a red potion, which turns his eyes turned red and transforms into Yin in a red hue. He controls the female puppet who turns out to be his sister Yan.
yin and yang are concepts used to describe how apparently opposite or contrary forces are actually complementary, interconnected, and interdependent giving rise to each other as they interrelate. Many tangible dualities (such as light and dark, fire and water, and male and female) are thought of as physical manifestations of the duality of yin and yang. This duality lies at the origins of many branches of classical Chinese science and philosophy, as well as being a primary guideline of traditional Chinese medicine, and a central principle of different forms of Chinese martial arts and exercise.In Chinese philosophy,
Yin is the negative/passive/female principle in nature, and may allude to many other concepts e.g. the moon, shaded orientation, something covert or concealed, "of the netherworld", overcast or sinister.
Yang is the positive/active/male principle in nature, and may allude to many other concepts e.g. the sun, open, overt, and "belonging to this world".