User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-67.176.158.104-20140207023318/@comment-16281343-20140207042906

When Saji uses Vritra Promotion, he does fit the description of JD or BtB. Although of course with Vritra guiding him, he can control it in the future.
 * Releases or uses all of its power. (Where he can use all of the abilities of his Sacred Gears all at once)
 * Gets into a berserk state