Mark Twain is a very fun and extroverted person, caring deeply for his friends, often even asking them to hang out after work which they usually refuse. He often makes jokes and is generally very lighthearted and laid-back, it's rare to see the man serious but when it comes to his weapons he can be; on missions he actually focuses. He's quite prideful about his abilities even keeping track of his successes in his "success diary" though he can acknowledge when others best him. 