It was natural for the metamorphosing red reiki to have a higher quality than white reiki during the Foundation Establishment Stage. From training the body to expanding the sea of reiki to drawing talismans, the red reiki was infinitely more powerful than the white reiki. Its strength was simply on another level.
However, after Akie Hanzawa had fulfilled his obsessiveness, the remaining amount of reiki was too massive. It would be impossible to assimilate it with the white reiki in his body. Kazuki was worried that the white reiki in his body would instead consume the red reiki.
Then, the red reiki traveled towards the sea of reiki. With the sea of reiki as its center, it flowed to every part of Kazuki's body. Suddenly, the red reiki coursed through his every vein and expanded his sea of reiki.