Asanuma is an overweight man of average height. He is seen wearing a navy blue shirt under a blue track jacket with a white stripe going down the sleeves. He also wears long beige shorts.
His cowardly nature is revealed when he is repeatedly the last member of his group remaining after the other two have been incapacitated. When he realizes he has lost, he does not hesitate to whine and beg to be spared.
Dollars/ Mika Harima ArcEdit
Asanuma is an accomplice in the kidnapping of Rio Kamichika. After Morita leads Rio to the back of the van and Kanazawa drugs her with chloroform, they drive to a parking garage to deliver the kidnapped girl to the buyer. After waiting for some time, the Black Rider appears. Kanazawa is the first to attack, and Celty rams his head into a concrete wall with her bike. Frightened, Asanuma climbs back into the van and starts the engine while Morita jumps into the back. Morita tazes Celty as she drags him out of the van. Celty quickly recovers and slams his head into the back windshield, knocking him out. Asanuma drives away, panicking, only to have Celty follow him. After a being chased for some time, he abruptly stops, making Celty crash into the back of the van and causing her to fall from her bike. Her helmet comes off when she hits the pavement. Celty stands up and summons her scythe with her shadows and slashes Asanuma, causing him to fall unconscious.
Asanuma and his crew later kidnap Kazutano from a building where undocumented immigrants have been living. When Kanazawa spills chloroform on himself, all three kidnappers become sleepy. Asanuma and Morita leave Kanazawa behind with Kazutano's cell phone in his pocket, allowing Kyohei's gang to find him. Kyohei calls the other two kidnappers to learn the meeting location, resulting in a car chase with Saburo in hot pursuit of Asanuma's van. With Celty's help, Kyohei's gang manages to corner the kidnappers and rescue Kazutano. Asanuma tries to climb a fence to escape, but Kyohei pulls him down. When Asanuma refuses to talk about his employer, Kyohei allows Walker and Erika to torture him. From him, they learn of the human experiments conducted by Yagiri Pharmaceuticals.
- Asanuma is repeatedly the last member of his group remaining after the other two have somehow been incapacitated.