Now why would Nea promise to remain the Earl’s “ally” (note the original text is 「何があっても味方だから・・・」 so this should be “ally” or “ON your side,” and not “by your side”) “no matter what happens” and then go on the run with Mana? Nea in this flashback is most likely speaking to Mana, and the way this is drawn, it looks like Mana’s memory. The Earl is losing control over Mana.
We know that after an undisclosed period of time on the run, the Earl eventually killed Nea. But in chapter 218, the Earl says everything was Mana’s fault: 『すべての元凶は”マナ”だッタアアアアアア!!!』 Once again, why did the Earl kill Nea and even their mother but not Mana?
Remember what Cross said in chapter 167? The day his brother died, Mana lost his mind. We know he’s wracked with guilt from Allen’s hallucination of him asking Nea: “Do you hate me?” (212) AND the Earl’s hallucination of Mana saying “Nea… I am sorry, Nea…” (218).
In chapter 188, we have the Earl crying over “that time” with the 14th and then asking Road to keep it a secret. Right after that, he dons the suit while uttering suspiciously Mana-like words:
Earl in 188: 「何があろうと立ち止まることは許されない」
“No matter what, I can’t allow myself to stand still.”
Mana’s words to Allen: 「立ち止まるな、歩き続けろ。」
“Don’t stand still. Keep walking.”
Remember Mana’s words to Allen also happen to be Nea’s dying words to Mana, according to Road in chapter 205. If the Earl is Mana, he’s simply repeating the very words his brother told him.
COMMON CRITICISMS OF MANA = EARL THEORY:
Mana & Earl in same place at once…
1. Graveyard flashback (Mana becomes an akuma): Allen calls for “Mana” and then we have a “Mana Walker” (note the conveniently mistaken name so the Earl couldn’t know who Allen meant) Akuma but the Earl steps out to lunch. What happened? Why didn’t he attack Allen when he turned out to be an Exorcist? Even he doesn’t know. I think Mana’s soul (or part of it) went to the Akuma, and the Earl froze/got stunned/lost focus at this point where he’s weirdly stylized: