Viridian Green

Prior to Soseki Natsume moving into the Garridebs' complex, Olive Green was enrolled in the Thorndyke Academy of Fine Arts. She was also engaged to the previous owner of that flat, a fellow student named Duncan Ross. After a series of gas leaks began occurring in his flat, Green begged him to move out.

Ross assured her that he would, but ended up dying due to gasoline asphyxiation before he could, leaving Green overcome with grief. She regretted not trying to persuade him hard, and she dropped out of the school and would walk by Briar Road, where Ross had died, many times.

One day, she saw Natsume come out of the complex and followed him to the borscht shop. He told her he had complained to the owner about how he often woke up the with the gas stove turned off and the room filled with gas, leaving him feeling like he was being strangled. Although she initially thought of Ross' death as an accident, she became suspicious of the other tenant, William Shamspeare, as she had heard that blowing with considerable force into a gas pipe would extinguish all flames in another room, resulting in a gas leak. She formulated a plan to confirm her suspicions.

After purchasing a bottle of strychnine off the black market, she anonymously sent Shamspeare a note that read: "I have information regarding the death of Duncan Ross. Come to The Slug and Salad, on Briar Road at 5 p.m. on 17th. Don't tell anybody else about this letter or the meeting. It is a matter of utmost importance." On that day and after Shamspeare had left his bedroom, she picked his lock using a wire and some turpentine (a trick her late lover had shown her), and coated the lamp line with the strychnine.

That way, if Shamspeare tried blowing into the pipe again, he would poison himself as punishment and would prove he had been blowing into the pipe. If he was really innocent, nothing would happen, but she prayed that he would be poisoned.

She also found a hiding place under a set of loose floorboards, which contained a tin box with a key and a newspaper. Thinking the key was valuable, she put it on like a necklace.

Naruhodo interrogated her for a few minutes before he was called away, as Shamspeare had finally fallen victim to the strychnine. However, it soon transpired that he had actually survived, and had accused Natsume of the crime.

After the first day of the ensuing trial, Green was to be discharged by her doctor. Shamspeare stumbled into her room and commented on her painting, making her feel worse. With her mind racing, she attempted suicide by drinking the remaining strychnine from her bottle, but was interrupted by Naruhodo, Mikotoba, and Sholmes, who were all visiting her again.

She was especially shocked to hear that the three had learned of her connection to Ross, causing the bottle to fall over and spill the strychnine. A foraging mouse then consumed the strychnine and died instead, thus causing Sholmes to deduce her suicide attempt and confiscate the bottle from her.

Later, Naruhodo called her as a witness in the trial's second day. Though the true extent of Green's crimes were exposed, it was also thanks to Green's help that Naruhodo was able to also expose the true extent of Shamspeare's crimes. Green would have to face charges for her attempted murder, but she nonetheless thanked Naruhodo for finally revealing the truth behind the "cursed lodgings" mystery, thus properly avenging her fiancé's death.