To help.

Helping is a little different from cooperating—this is about granting a friend's request or call for help. Unbeknownest to the boy and girl, Allen did a risky "helping" procedure.

The journey to find General Cross had started. The team found a clue on Cross’s whereabouts in China. They went to a love brothel owned by a beautiful woman named Anita, the general's latest lover. Anita and her staffs were also supporters of the Black Order. Anita told them that, unfortunately, Cross was no longer in that place. He had left for Edo, but his ship was sunk. Allen believed that his master was still alive, so they should go to where his master was headed. Anita had her staffs prepare a ship to sail on.

While they were making preparations, Allen's eye detected a bunch of Akuma heading their way. Allen ot snatched and almost fell down from a great height, but Lenalee came to rescue him—since her Innocence supported her to fly as she wished.

Allen and Lenalee found out that the akumas were after a strange, giant object—which Lenalee later recognized as Suman Dark, an exorcist who was said to be "missing" while his party members had been confirmed dead. Suman had turned into a Togaochi. She told Allen about her unpleasant memories about Togaochi, and said that they should help Suman.

Being a good friend he was, Allen held Lenalee and tried to calm her down and went to Suman. However, they got separated because Allen got sucked into Togaochi. He had a rough time trying to save Suman—the guy was already filled with hatred and despair. Allen invoked his Innocence to maximum and finally convinced him to go back. However, when the strange object was gone, Suman's body no longer breathed.

Afterwards, Tyki Mikk arrived. Tyki killed Suman and attacked Allen instantly, dissolved Allen's left arm from his body. He mentioned that he was looking for the Heart. If Suman's Innocence perished when he destroyed Allen's Innocence, then Allen's Innocence was the Heart. Tyki then destroyed Allen's Innocence, but there was no reaction on Suman's.

Allen asked Timcanpi to take Suman's Innocence to where everyone else was. Tyki then 'killed' Allen using a butterfly-like creature named "Tease". That thing made a hole in Allen's heart without leaving external wounds. Allen was unable to fight back at all, he just lied there, unconscious.

Meanwhile, Lenalee was desperately looking for Allen. She and Lavi met Timcanpy on their way, so the golem guided them to where it parted with Allen. There were traces of Allen's blood, but his body was nowhere to be found.

Later, a messenger from Black Order Asia Branch named Wong came and told them that they had found Allen's body. Lenalee was relieved upon hearing that, and asked Wong to let her meet Allen. However, Wong said that she couldn't. Moreover, Allen had lost his Innocence so he could no longer be a part of the team, so they should go on ahead without him.

When we look at it again, why should Allen try to fulfill Lenalee's wish to help Suman? Of course, this is because what Lenalee told him about "the world". Allen hadn't even met Suman before, but he knew how meaningful her comrades meant to Lenalee. Therefore, he tried to help her saving Suman without knowing much—the Fallen could not be saved, because they betrayed their Innocence. Should Lenalee or Allen knew about this, maybe they wouldn't have attempted to rescue him in the first place.

It is understandable that Lenalee blamed herself for this—she was the one who said that they should help him, but hey, that was not her fault. Lenalee was not the only person who would like Suman to come back to the Order. Johnny, for example, said that he liked playing with Suman. Naturally, all the Exorcists are "family" members of the Black Order since the headquarters became their new home, and it was completely right for a family, or a friend, wanting to help someone else who were troubled. It was just that they didn't expect the result would be something bad.