User blog comment:Crimson and Darkness/Shin DxD 3 discussion/@comment-36663391-20190823203205/@comment-35679297-20190823220207

The only way for Issei of unlocking GR's is to awaken Infinite power inside him, even with the power of.GR unlocked m, Ophis said that DxD is the final form of Issei so Ryuuteimaru wanted to help Issei to become stronger since UL comes earlier that planned and that Issei is too weak at the moment for fighting them