Ten'i Seikouki

"It's not about powering up. The point is that he won't have to power up when he fights. He can use all the energy it would take to transform, to instead increase his chakra and stamina, only needing to go higher if he needs to. Damn... it's so ingenious."

- Ryun Mazuka

Ten'i Seikouki (リラックスした神聖なエネルギー, lit. Relaxed Sacred Energy) is a state of Seikouki, that is taking the form a step further, but in it's entirety, a completely different state. Instead, it is a state of mental and physical perfection of the core Seikouki state itself. The only confirmed physical difference is that Seireitou's facial features exhibit less tension and ferocity than the regular Seikouki form, which can be explained by the mastery over the chakra consumption and the emotional restlessness that the regular Seikouki transformation causes. The aura is also noted to be different. The aura is also seen to be less violent than the Seikouki, but not as gentle and flame-like as the original form as normally seen. In this form, his physical form doesn't change at all, but his eyes become clear crisp golden, and his hair gains a slight lavender tint to it.

In the real world, athletes who train in aerobics for extensive periods of time experience heightened states of rest: heart and respiratory rate are much lower than that of a normal person. The Ten'i Seikouki transformation follows a similar fundamental concept. By remaining transformed for extended periods of time, the user can desensitize themselves to the negative effects of the transformation. Their wild emotions are kept in check, resulting in a more strategical fighting style, and chakra consumption is reduced to negligible amounts. Energy radiation is reduced in tandem, and the aura takes on a smoother, flow-like appearance. By mastering the transformation, the user is able to retain transformation almost subconsciously. In requiring less ki to contribute to maintaining the transformation itself, the maximum amount of chakra can thus be focused into the attacks giving the user access to power greater than that of even a master of the ground state of Seikouki. It was in this way that Rikudou has said that Seireitou has surpassed his ancestor Unagi.

The key to the Ten'i Seikouki state is chakra conservation rather than boosted energy output. This results in a person who is able to fight longer and more efficiently than with the basic Seikouki form, and can even remain transformed for days without powering down as long they don't expend too much energy, essentially making the transformation the user's base form.

Trivia

 * The Ten'i Seikouki is based on the principles of meditation, and influenced by the Full-power Super Saiyan form in Akira Toriyama's Manga series Dragon Ball Z.
 * It is unknown if Rikudou ever took Seikouki to this state, even given his supposed mastery of the ground state. However, given his declaration that Seireitou has surpassed Unagi upon attainment of this state, implies that Rikudou himself never obtained it either.