Was Mephisto aware that Yukio had Satan's blood in him after all?


On Episode 6 of **Ao no Exorcist** , at around 21:30, Principal Mephisto
Pheles tells his younger brother, Amaimon, to pass on a message to their other
siblings. If the subs were right, it says: _"...tell our siblings who are
going mad with envy that our youngest brother is being raised under my wing"_.

![Ao no Exorcist Episode 6](https://i.stack.imgur.com/mVdhd.png)

On episode 23 however, Yukio offers his own _Satanic_ blood to open the
Gehenna gate, and at around 2:40 we can see Mephisto and Amaimon observing the
chaos unfolding from above. Being the younger twin, Yukio is technically their
youngest brother with their blood - in contrast with their conversation from
episode 6. They do not seem shocked by the news that Yukio possesses Satan's
blood after all, or they cleverly hid their reaction.

![Ao no Exorcist Episode 23](https://i.stack.imgur.com/JqXjy.png)

I am asking for clarification, preferably from manga readers: Was Mephisto was
really aware of his erroneous statement and was it all really part of his
_plan_ or is this merely a (gasp!) narrative plothole of the anime?




I'm not sure if it's a plot hole but it's definitely a bit dubious. Yukio's
body wasn't strong enough for Satan's powers, so they rejected him leaving him
a pure human.

But Satan is still his dad, so I guess he might still have inherited stuff
other than demonic powers. Maybe that includes Satan's blood type, assuming
Satan has blood.

There aren't really any answers in the manga, because the anime goes in its
own direction after episode 16 or so, but to answer the question, yes
Mephistopheles definitely knew he was the son of Satan but that he had no
demonic powers, no he almost certainly wasn't talking about him when he said
our youngest brother.




I'm not sure if it's a plot hole but it's definitely a bit dubious. Yukio's
body wasn't strong enough for Satan's powers, so they rejected him leaving him
a pure human.

But Satan is still his dad, so I guess he might still have inherited stuff
other than demonic powers. Maybe that includes Satan's blood type, assuming
Satan has blood.

There aren't really any answers in the manga, because the anime goes in its
own direction after episode 16 or so, but to answer the question, yes
Mephistopheles definitely knew he was the son of Satan but that he had no
demonic powers, no he almost certainly wasn't talking about him when he said
our youngest brother.

