This techinque was created by Ogata Isshinsai. It is a very dangereous technique from the Ancient Martial Arts, Seidou Gōitsu combines the opposing ki of both Sei and Dou, by having the first being focused inward, while having the second explode outward. The result is an explosive boost in all of the user's physical capabilities and increased effectiveness in the user's martial arts techniques. However due to the conflicting nature of the ki of Sei and Dou, extensive use of this technique causes a disruption in one's flow of ki resulting in crippling, even fatal damage to the user. Ryūto had experienced tremendous stress after using Seidou Gōitsu, to the point where both his hair turned white and one of his sclera turned black permanently and was temporarily bound to a wheelchair due to his legs being too damaged to support him. However if one manages to regain control over their ki, they can reverse the physical damage caused by this technique.
According to Isshintai Ogata, this technique can only be taught to a small number of fighters who have a natural ability to use both ki of Sei and Dou. Examples include Ryūto, Shō Kanō, Rimi who have learned this technique; though Ogata also stated that Kenichi has the potential to learn and use this technique. Ogata also noted that in order to use this technique without the devastating side effects, the user must keep their emotions under a very tight control, which he also noted to be the reason why Kanō was able to use this technique so effectively, due to him being raised under great isolation and emotional control. Ryūto was also able to gain control over the technique and can now use it for 30 seconds without any physical side effects.
Recently, after long absence, Ryūto used the Seidou Gōitsu against a weapon user master. However, it is unknown if he perfected it or not. Ogata the creator of the technique was finally shown to use it in the final battle against the Ryōzanpaku masters, who were allied with Cyril Rahman, Agaard Jum Sai and Sōgetsu Ma during the Eternal Sunset Arc. Ogata was able to defeat Cyril Rahman, who described the technique to be evil.
Because of the powerful fusion of both Ki types in one person's body, this technique can level up the user far beyond their normal level of skill and power. It gave Ryūto and Rimi, who are both at the level of a High Class Disciple, power almost comparable to that of an Expert. It can also give Ogata Isshinsai, who created it, power that brings him close to the level of a Legendary Master. This was clearly shown due to the fact that Ogata defeated two Grandmasters, Rahman and Agaard, who are considered powerhouses in the martial art world within seconds, one after another. This is one of the most impressive feats in this series, as Agaard's fighting prowess has been fully portrayed many times and it's consistently on par with the skills of other Grandmasters.