Twain has dark orange hair which is swept outwards and green eyes. He wears a long white sleeve shirt with buttons that are always undone and black pants with the suspenders down. He wears black sandals and black bracelets around his ankles. On his left wrist are two brown bands.
Twain is generally a jovial and cheerful individual, in contrast with most of his fellow Guild members. As such, he would usually suggest that they go on excursions to spend some leisure time when given a chance altogether, but they would simply reject his idea in the process. Nonetheless, he is quite close with them until the organization's eventual dissolution, considering the Guild to be a rather nice place.
As one of the Guild's snipers, he takes considerable pride in his marksmanship and ability, wherein he keeps a personal record of his endeavors that utilize such skills in his "success diary". Twain would also frequently dote on his doll-like companions Huck and Tom for their skillful marksmanship.
Despite this lighthearted attitude, Twain can become serious at times during combat, especially when dealing with an opponent who challenges his sniping skills like Atsushi Nakajima, whom Twain has admitted to be the strongest adversary in his success diary. In spite of his confidence in his own skills, it is not impossible for Twain to acknowledge his opponent's expertise. Hence, he easily and amicably accepts defeat when he is apparently bested by such adversary.
Huck Finn and Tom Sawyer (ハック・フィン&トム・ソーヤ, Hakku Fin & Tomu Sōya?) is an ability that takes the forms of the doll-like creatures known as Huck Finn and Tom Sawyer.
With his ability, Twain can shoot with absolute accuracy by attaching either Huck or Tom to one of his bullets. Since Huck's and Tom's minds are also linked, he can perform long-distance surveillance using them.
Little is known about Twain, and his life before his membership in the Guild nor his reasons for joining it are not specified. However, it is quite possible that he has worked on his success diary for quite some time, most likely having started it back in his hometown.
After the Guild war, he and the other Guild members were discussing the fate of the Guild. Twain decides to return home in order to finish his own autobiography.
- Twain appeared in the Japanese mobile game Love Heaven along with several other characters as a limited-time event.
- Twain shares his birthday with another Guild member, Lucy Maud Montgomery, on November 30.
- Twain is thus far one of the two characters with an ability that has more than one different references to its name (Adventures of Huckleberry Finn and The Adventures of Tom Sawyer). The other ability user with a similar case is Edgar Allan Poe, whose ability is a reference to two stories.