Episodes 7-9 of the Soukyuu no Fafner: Dead Aggressor - The Beyond series.

An innocent young man, Ikuroo, has a parasite known as Baoh implanted in his brain by an evil organization, Doress. The parasite makes him nearly immortal and gives him the ability to transform into a really powerful beastie when he's in trouble. Doress intends to use him in some sort of ploy for financial success, world domination, or something along those lines, but when they're transporting him on a train, a young psychic girl, Sumire (who's being held by the organization due to her abilities), sets him free and the two escape together. Of course, Dr. Kasuminome is the mad scientist behind the whole Baoh thing, and he isn't about to let his test subject get away and he has considerable resources (including some superpowered lackeys, as well as a small army) at his disposal.

Sendo Kazuki, failed the entrance exam for the art college he was applying to, His childhood friend, Kuhonbutsu Taishi forced Kazuki to enter the doujin (private publishing) world.

A terrible war has ravaged the land, and now, fueled by the blood of numerous fallen warriors the Yoma, demons from hell, emerge once more. A skilled ninja seeks to end the bloodshed these demons inflict upon humanity, but to do this he must fight against his undead former best friend and fellow ninja who was killed in battle and has been resurrected to serve the Yoma.