Izanagi seems like the logical choice, but i just want to makes sure. did obito uses kamui to let the flames phase through him after contact or did he used izanagi? i think he used izanagi for 5 reasons.
1. he could 2. said he kept it secret which is why he survived it. (itachi knows about kamui) 3. the flames hit and followed as obito walked back. so he wasn't intangible 4. he screamed in agony implying the flames did hit. wouldn't happen if kamui 5. in the dark area, it was silent for a sec. then obito returned. like izanagi
there was better reasons written by others, but i don't want to steal their glory