Akechi is a young detective with amazing abilities and personal skills. He is just a student, but everyone can recognize how smart and capable he is. He is the last person to join the main party and his main Persona is called Robin Hood.
He has a handsome appearance and girls love him. Everyone loves him, but the truth is behind his behaviour. He studies the case of the Phantom Thieves and once he found out that their real identities are the ones of Akira and his comrades, he joins them in order to follow a personal plan. His truly identity is Shino's illegitimate son. His mother suicided once she was abandoned by his father, and he lived his life to take revenge. So he used the Phantom Thieves and his ability to menage to use two Persona, to reach his father and make him pay for his mother's death.
True is that even if everyone praises him, Akechi doesn't love himself. He thinks that evryone is a fake. And even if he smiles and says Akira that they are friends and he is happy to work with them, he truly hates and and is envious of their strong bond. He never felt like he was part of the team. He thought he was alone among them instead. Because he never thought that someone could have possibly loved him for what he truly is. Futaba explains him that he has good sides too. And he is a friend. Also, he has amazing abilities that not everyone has, so why not loving himself? Akechi gets berserk after revelaing them the truth and finally uses his real Persona, Loki. His costume is black and he took his mask of kindness and smiles off. Now he is totally fool and his only desire is killing everyone to finally reach his father. Anyway, he loses against the Phantom Thieves and they invite him to join forces again, but Akechi looks confused. He can't believe he can really be loved by someone, and can't trust them. While he was about reflecting, a copy of him try to kill him with a gun. It's a copy bron from Shino's thoughts about him, so Akechi finally finds other truth about himself and what his father really thinks. The copy even tries to "give" Akechi the chance to survive killing all the others, but since Akechi finally seems to have understood what Anne and the others told him, decides to sacrifice himself in order to make the others free to reach his father and trying to change his heart.
We do not know what happened to him after that last battle he did using his Loki, but Futaba sais she lost his signal. There is no way I can think he is dead. His story still needs to be explained and he has not a resolution. So I hope we'll get some other new game about this Persona, that is very very amazing.
I love Akechi and I wish with all my heart to see him again soon!