[His eyebrows raise at him mentioning that he won't age, but... that makes sense, doesn't it? He's just.. a soul now...

He draws in a breath, looking over for a moment in thought, before his gaze returns to Akechi.]

Shapeshifting alters your appearance, and you already have some experience in that. Perhaps... it'd be possible to learn how to alter your appearance so that you seemed older? Given that I saw someone here finely alter the size of their wings... I imagine similar concepts would apply for tuning your physical appearance.