13 is often seen wearing a hat with a stripe down the top, a worn jacket with spikes on the shoulders, a plain, grungy t-shirt with the number "13" on the front, tight pants, and some sort of skirt like item that appears to be plaid.
He has two red stripes on each of his cheek, sunken eyes with small pupils and large bags underneath, and pointed teeth. 13 has dirty blonde hair that is fairly short and unkempt which reaches the back of his neck.
13 is very laid back, but seems to be very emotional if his reactions are anything to gauge by. He is quick to react with extreme emotion such as irritation, fear, anger, and occasionally more joyous feelings. 13 is somewhat of a coward and often shies away from danger. He shows romantic interest in Nikaido early on, though not as seriously as Kaiman's clear attachment, but later in the series it seems to simmer into more of a loyalty of friendship.
13 is initially introduced as a regular at Nikaido's restaurant, coming in to eat some gyozas (automatically putting him at odds with Kaiman, who defensively wants to hoard all the gyoza for himself). Vaux also appears and is sulking about how the hospital baseball team will unable to play against the Sharks unless they find another player, which leads to 13 offering to play for them.
In the match against the Heiwa Clinic Sharks, 13 asks Kaiman what kind of relationship he has with Nikaido, who simply replies that they are friends. 13 then asks if he would mind if he tries to ask her out, and Kaiman dismissively tells that he can always try. Nikaido is up to bat and Fujita (playing as the pitcher for the Sharks) is so pissed of about her presence that he aims directly to her head. 13 is concerned over how little Kaiman seems to care about that, but Kaiman tells him that he should know Nikaido better, and is proved right when Nikaido is able to get such a hard hit off the next pitch that she injures someone and the game had to stop.
13 appears once again after Kaiman leaves Hole to go to the sorcerers' realm, where he comments on how crowded the Hungry Bug is. He congratulates Nikaido on the business success, and she replies that it's all because Kaiman isn't there to scare away customers.
During Dr. Vaux's birthday party Nikaido, the doctor, Kasukabe, Jonson and 13 were celebrating when the professor finally reveals that Nikaido is in fact a Magic User. 13 is the only one confused and scared by this revelation, but doesn't get much of a chance to process it.
The group is then attacked by a mushroom monster grown from Nikaido's back. She was able to destroy it, but all 5 party members where teleported to En's mansion in the magic user world. Before 13 could do anything, his head was transformed into a big mushroom by En and everyone was imprisoned in cells inside the mansion.
13 spent days sitting in a cell along with Kasukabe and Jonson, not knowing what was going on due to not having eyes in his mushroom headed form. In the end, thanks to Jonson's ability to speak with other cockroaches he was freed along the rest and ultimately was healed by Noi once Kasukabe and Shin met again.
After a party to celebrate the reunion between the doctors and Shin, 13 and the rest disguised themselves as Goons and stole a minivan to go and find Kasukabe's Wife in the Hydra Forest. They believed she could help deliver a message to Kaiman to let him know what happened to Nikaido and have him save her from En.
When they arrived at the cabin, they where ambushed by some gruesome Frankenstein-like magic users with crosses over their eyes. One of them injured 13 with a machete and Kasukabe told Vaux to grab the wounded young man and hide anywhere in the cabin while he and Jonson dealt with the sorcerers. The doctor and 13 hid in a storage closet for such an extended time they started to wonder if everyone forgot about them.
Once the cabin was destroyed and they were all saved by Shin, Kasukabe revealed that he had already managed to meet with his wife. The group went back to the mansion and Kasukabe told the cleaners about what he had seen in the cabin. Eager to find clues about "The Cross-Eyes Boss" Shin and Noi accompanied the humans back to Hole. 13 was happy to see his world again, and kinda grossed out over the spoiled remains of Vaux's birthday party, due to them being away for quite some time.