Lin Yao first appears in chapter 32 of the manga, in a confrontation with the Elric brothers. Due to the declining health of his father, the Emperor of Xing, Lin left his country to find the Philosopher's Stone to stabilize Xing, as well as grant him the key to immortality. Although he is the 12th son of the Emperor, Lin hopes the Philosopher's Stone will help him rise in the order of succession and achieve the throne thereby securing his clan's welfare.
When he first appears, Lin aggravates Ed by following him around, charging his huge meals to Ed's tab and flirting with Winry (and being taller than Ed). The fact that he is also searching for the Philosopher's Stone leads to conflict with the Elric brothers. Despite this, Lin becomes an ally and friend after he helps Maria Ross escape false murder charges and providing sanctuary for her in Xing.
Although Lin often behaves in a laid-back, goofy and downright undignified manner, he is a skilled fighter and keeps a cool head in battle. He arrives in Amestris with two bodyguards, a young woman around his age named Ran Fan and her grandfather Fu, whom he sends back to Xing with Maria Ross. Their loyalty to him is absolute with Ran Fan going so far as to cut off her arm as a decoy that allowed the two of them to escape from Wrath/Bradley and Gluttony.
Lin's true honor shows through in a fight with Bradley (chapters 46 and 47), by refusing to abandon Ran Fan despite her injury and inability to fight slowing him down, and by arguing with Bradley about what makes a "true king." Lin is a devout believer in fealty, that is, that a king needs the support of his people, and without the people, there is no king. Bradley responds that there is no such thing as a "true king," and that the sole purpose of power is power. To him, people are only a means to power and if they will not, can not, or can no longer provide it, they should be discarded as one would anything else without use.
Lin is known for fainting from hunger in the middle of the street, which led to his first meeting with the Elric brothers and Winry, and to his arrest by the Amestris military police.
In chapter 63, Fu explains that the Emperor's condition is deteriorating, and Lin must be brought back to Xing as soon as possible. Some of Greed's distinctive facial features appear to be manifesting in Lin as well, as his eyes, nose, and jawline have changed dramatically.
Greed makes a brief appearance at the end of chapter 73, with a pair of chimeras. He appears again in 74, in a short conversation with Pride.
In chapter 82 Greed kills Bido, his old friend from the Devil's Nest. When he does, his Ouroboros symbol is covered in blood; and in the same manner as Alphonse, he regains his old memories as the old Greed. Specifically, that Wrath was the one who had killed him several times as well as all of his friends. In a state of madness and rage, he attacked Wrath in front of Wrath's family. However, Greed fled upon remembering his and Lin's past battles with Bradley. He then manages to reach the old dilapidated cottage where Lin had been when they had caught Gluttony. He faints to the floor as Edward finds him, however he had reverted to Lin. Ed feeds him, and they talk about Lin's situation and info relating about Father's plans, but as he was going to say the date when the plans were going to be set in motion he reverted back into Greed. He then realised he had nowhere to go, since he couldn't go back to the Homunculi. Ed invited him to join their side, but Greed was not willing to follow anyone. Instead, Ed then decided to work for Greed instead, for the time being. Ed also stated that Greed and Lin would both be called "Greelin".