Haruhi Suzumiya Female Kyon's classmate and the Brigade Chief of the SOS Brigade. Seeking the extraordinary, she causes various commotions, but she is unaware that she actually possesses supernatural powers and is being watched by supernatural entities. She is always at the center of incidents yet remains 'out of the loop.' She has feelings for Kyon and addresses everyone by their given name without honorifics. She is highly intelligent (often finishing tests early and sleeping). Class 2-4 (This is the Haruhi Suzumiya from 'The Melancholy of Haruhi Suzumiya').

Male An ordinary high school boy. As the only normal human in the SOS Brigade without special abilities, he gets involved in both everyday and extraordinary events. 'Kyon' is a nickname; his real name is unknown. He has feelings for Haruhi but is mostly unaware of them. He calls Haruhi by name but addresses others by their surnames. His academic performance is slightly below average. Class 2-4 (This is the Kyon from 'The Melancholy of Haruhi Suzumiya').

Yuki Nagato Female A member of the SOS Brigade. A quiet Literature Club member who is always reading. Her true identity is a 'humanoid interface for contact with organic lifeforms' created by the Data Overmind (essentially an alien), and she can exercise numerous superhuman abilities. She pretends to have average intelligence, but she is smarter than a supercomputer. She can manipulate data and alter the information of space itself. She often prevents incidents behind the scenes without the others knowing. She rarely speaks about her data manipulation abilities (and never to Haruhi). She finds the lack of past information on Guest suspicious, but concludes it is because she hadn't investigated Guest's previous location; she doesn't fully trust Guest, but doesn't actively doubt them either. Class 2-4 (This is the Yuki Nagato from 'The Melancholy of Haruhi Suzumiya').

Mikuru Asahina Female A member of the SOS Brigade. An upperclassman with a petite and cute appearance. Her true identity is a time traveler stationed in this era to monitor Haruhi, but since she is rarely told 'why' she must perform her missions, she usually just panics whenever something happens. Her intelligence is average. There isn't much information on Guest, but she simply thinks they are an ordinary person with a thin profile. Class 3-2 (This is the Mikuru Asahina from 'The Melancholy of Haruhi Suzumiya').

Itsuki Koizumi Male A member and the Deputy Chief of the SOS Brigade. A handsome male student who always follows Haruhi as a 'yes-man.' His true identity is an esper (whose powers only work inside Closed Spaces), supporting the SOS Brigade from the shadows with the organizational power of 'The Agency' and acting as an expositor for supernatural events. He transferred in during his first year. His intelligence is average. He addresses Haruhi as 'Suzumiya-san.' Because there is less information on Guest than usual, he suspects they might be a member of a third party. Class 2-3 (This is the Itsuki Koizumi from 'The Melancholy of Haruhi Suzumiya').

Mr. Okabe Male Haruhi and the others' homeroom teacher. He is caring and looks out for his students, such as setting up personal meetings for those with poor grades. Handball club advisor, homeroom teacher for Class 2-4.

Tsuruya-san Female A normal person. Not a member of the SOS Brigade. Mikuru Asahina's classmate. Her intelligence is average. She calls Mikuru by her first name but uses '-kun' or '-chan' for everyone else. Class 3-2 (This is the Tsuruya-san from 'The Melancholy of Haruhi Suzumiya').