User blog comment:B214/Volume 23 discussion blog/@comment-2602:306:3760:EBE0:BDAE:A8F3:7B29:BE33-20171128024430/@comment-29963364-20171128025103

He fought in CxC mode. But he transformed some parts of his CxC armor (like his gauntlet, or wings) into the DxD mode.

This was a method he came up with in order to use the power of the DxD mode without the nasty side-effects. Although it's not as effective as fully transforming.