Cr1ms0nReader
I would go for Bleach!! For a couple of reasons. 1. Bleach is all about Souls and soul power manipulation, sacred gears are about souls in symbiosis with their host souls, which is oddly familiar to how the soul slayer weapons are. This can help in his research to better understand and improve his first sacred gear. 2. Bleach is mostly about swords and sword skills that manipulate soul power to perform fighting techniques that that are usually stronger than either alone. 3. Sephiroth could also study his magic and merge it with soul power to produce way stronger magic and could be the missing link in combining Magic + Senjetsu + Chi (Touki) + Soul Power = new power base that is probably one step under True Divine power. You could think of Soul Power as Base or stabilizing agent for the volatile synthesis from before. But it would not be piece. Think of it like this. Soul Power links to the soul, Magic the mind, Senjetsu the world, Chi or Touki to life and body. Or at least that's what appears in my head. It may not perfect it but give a vital clue for progress. 4. Naruto's world would be the final key as it is a world where mental power meets and blends physical power to make Chakra. 5. If he goes to naruto first, he already has experience with Senjetsu and chi and would adapt fast, He would still be overpowered for the world. 6. Naruto's Chakra though the big missing piece, will not bring him the biggest gains. Yes chakra is a mix of spirit and physical energy but it hardly ever ventures into the spirit / mind part of that energy base. Bleach with all of its power based in the soul would net him more returns. 7. If he goes to Naruto's world after Bleach, then not only will he have a wider aspect on view of the different power-bases, but more importantly Better perfected control and manipulation over all his different power bases. 8. Where Bleach helps with in dept research with the soul, which is more inclined to his goals, Naruto may perhaps be closer to a cultivation world stuck in the foundation stage. Naruto got 2 things going for it. Doujetsus and the 8 Deadly Gates. 9. If he goes to Naruto's world after bleach, he could research and implant perfect Doujetsus, and study the chakra systems and how the 8 deadly gates interact with different energy types.. By this point he could perfect his merged energy power base, and create something close to his own personalized cultivation technique that would help him reach god hood with out some stupid fruit. 10. Now think of this if Chakra is a mixed blend of mental / spiritual power and physical power, then having absolute control in all aspects of chakra's power base would mean greater growth at a much more faster and better controlled speed. This would make Naruto's universe literally a vacation for him and his party. After he finishes and trains his group with what he learns, have him go back to DXD and OWN IT!! lol Then it might be time to chase the goddess. Maybe use Falna to increase his foundations to EX rank in all catagories to lv 12. lol Just break that world too. By then he could be ready for Saitama's world ONE PUNCH MAN! Nice chapter, and sorry for the dysentery. these are just my ideas. Good job on the chapter.