Characters

• Do-jin Kang — A former detective turned investigative journalist who chases urban disappearances and legends. With a blunt and persistent personality, he was the first to start tracking the Black Stain in the sewers. He acts as a mirror reflecting the protagonist's conscience and can become the only ally to dive into dangerous truths together. As he gets closer to the identity of the stain, he is exposed to danger and occupies a precarious position where he could be the first victim if the protagonist turns a blind eye to the truth.
• Boss No — The owner of the memory laundry and the protagonist's mentor. He has run the shop for many years while knowing the secret of the stains. He has picked the talented protagonist as his successor and intends to draw them deeper into the path of 'laundry.' He does not consider himself a villain, holding the philosophy that 'someone has to wash the dirty laundry.' He is both the greatest obstacle and temptation when the protagonist tries to uncover the truth.
• Yoon-ha — A repeat client in her late 20s who keeps coming back to erase the same memory. She carries a deep guilt that resurfaces even after being erased, and her memory is the key to the incident connected to the largest stain in the sewer. She usually appears quiet and exhausted, but breaks down in front of those she trusts. She is someone the protagonist wants to protect and the person who would be most hurt if the truth were revealed.
• Chairman Baek — A powerful figure in the city and a shadow client of the laundry. He is the true mastermind who entrusted his greatest sin to the shop, causing the stains in the sewer to overflow. He treats people with a kind and relaxed attitude, possessing the seasoned skill of delivering even threats like well-wishes. In the latter half, he steps forward directly to appease or crush the protagonist.
• Black Stain — A bizarre entity formed by the accumulation of erased memories in the sewers. It moves to find the owners of the forgotten sins and grows large enough to threaten the laundry and the city.
• Regular Customer — An anonymous client who frequently visits the shop. Represents the dry, indifferent atmosphere of the laundry where no one asks what is being erased.