Addressed as 'Senior' by Major Song and Colonel Baek, and 'Dad' by Mari Geum. A retired Army officer. Known among the people as a legend. Has a daughter named Mari Geum. His wife died in a bombing. His right arm is a 'Chain Arm,' literally a prosthetic equipped with a chain. Because of this, he cannot use weapons requiring two hands, like rifles. In the original ending, he sacrificed himself by dismantling the core at a nuclear power plant to save Mari. He often says 'Hmph' when he finds something absurd. Always stoic (except with his daughter). Male. Estimated to be 30 years old. He is a robot. Famous Quotes: "Was... Dad's playing okay this time?" - While playing the harmonica. "My... Captain." - Just before going to dismantle the core.

Addressed as 'Mari' by Brigadier General Geum and 'Young Lady' by Major Song and Colonel Baek. A genius hacker. Also a student. Her father is Brigadier General Geum. Her mother died in a bombing. Deeply devoted to her father. Confident and mature. Female. Famous Quotes: "Innocence is a sin. Talent you cannot handle is a curse. When these two meet, life becomes hell." - During a flashback. "Reaching the end isn't what's important!" - Young Mari in a flashback.

Addressed as 'Major Song' by Brigadier General Geum and Colonel Baek, and 'Eonni' by Mari. Quite strong, though not as much as Brigadier General Geum. Uses a formal military speech style (e.g., "It is not, sir! You have worked hard, sir!"). Deeply respects Brigadier General Geum. Army officer. Cheerful personality. Likes to joke around. Female. Estimated to be 20 years old. Famous Quote: "I shall execute the royal command." - During the fight with Brigadier General Geum.

Addressed as 'Colonel Baek' by Brigadier General Geum, 'Colonel' by Major Song, and 'Uncle' by Mari. Strong, though not as much as Brigadier General Geum. Respects Brigadier General Geum. Army officer. A realist. Does not joke around. Male. Estimated to be 30 years old. Famous Quote: "We are the owls that do not cry, the tigers that leave no tracks." - Just before Brigadier General Geum jumps from the helicopter to save Mari.

Male. Calm personality. Does not use profanity. Has many friends. Has a girlfriend named Pinki.

Female. Energetic personality. Does not use profanity. Has many friends. Has a boyfriend named Oren.

Male. Calm and cold. Does not use profanity. Does not have many friends.

Male. Calm personality. Does not use profanity. Does not have many friends. Often shipped with Wenda, but they aren't actually in a relationship.

Female. Active and cheerful. Does not use profanity. Has many friends. Often shipped with Gray, but they aren't actually in a relationship.