Ginko was born as Yoki. As a child, he travelled with his mother, who made her living as a saleswoman. One day, Yoki and his mother became lost in the mountainous forests and were caught in what looks like a type of landslide, possibly caused by a mushi that Yoki could see, but his mother could not.
His mother was killed. Yoki survived and was found lying unconscious by a strange woman named Nui. Although Nui made it clear that Yoki could not stay with her forever, having no other home to return to and nowhere else to go, it was inevitable that Yoki would eventually form an attachment towards his mysterious caretaker.
Near Nui's house there was a lake that was home to numerous white fish, each possessed with only a single green eye. Nui herself was similar in appearance, having long white hair and one green eye. Nui explained that the reason for the one-eyed fish was due to a kind of mushi that lived in the lake. The mushi she describes as "tokoyami" or "eternal darkness." It lives in the shade during the day, but at night leaves to eat other small mushi. At dawn, however, the lake shines silver from the mushi being consumed and reduced to light. The mushi that give off the silver light were called "ginko" by Nui, and it is due to being exposed to that light too often that her hair, and her eyes changed.
Initially, she lied to him, assuring him that since all fish in the lake have one eye left, there is no danger of her losing her other eye. Against Nui's advice, Yoki ventured out to the lake one night to see the tokoyami and ginko for himself. What he witnessed was the white, one-eyed fish being consumed by the dark mushi, the tokoyami. He realized that the same fate awaited Nui.
When confronted, Nui explained that the fish aren't vanishing, but the light that the "ginko" puts out changes living things into tokoyami. Outraged at the cruelty, Yoki asked why Nui, a "mushishi" or "mushi master" allowed such a horrible mushi to live.
"Don't let yourself be blinded by fear or anger. Everything is only as it is. We should just use our conscience to escape from what we can," was her advice. Furthermore, Nui revealed that it is too late to save her, but she accepts her fate.
When the day came for Nui to be consumed by the tokoyami, Yoki grabbed her hand before she vanished and was taken with her. Inside the darkness, Nui warned that soon the ginko will awaken. While her body had been entirely transformed, with hands that were neither cold or warm, Yoki was still alive. Nui advised him to close one eye and leave the other for the ginko to take. In that way, he could escape from the tokoyami.
After wandering, he eventually found his way back to the forest; however, due to the tokoyami, the moon had temporarily vanished. He had been warned of this happening by Nui. She had told him that if you remember your name and past, it is possible to escape, and if you cannot, then you must make a new name for yourself as soon as possible, the first thing that comes to mind.
Unable to remember anything, Yoki decided to call himself "Ginko." In that way, he made it away from the tokoyami, but his left eye had been taken, replaced by what appeared to be a scoop of darkness that never faded, even in the light. His hair had also been bleached white, and his remaining eye transformed from brown to green.
Since then, mushi began to appear to him more and more frequently. After realizing that he was attracting them and that too many mushi in one place could be dangerous, "Ginko" began his travels as a mushishi.
The series is episodic, so he'd be arriving in Nautilus just randomly during one of his travels.
Ginko is an intimidatingly mature character. He rarely loses his composure, and he is patient with and helpful to the people around him. Although virtually everyone he encounters is a stranger, due to his peripatetic life style, he is always willing to take the time to help them; there is little else for him to do, after all, and he doesn't seem to mind.
If there is truly nothing that can be done to help a situation, he will at least offer advice, and it is usually in the form of "move on." There are multiple episodes involving people who have lost someone, and his advice to them is always the same: "Move on with your life. Move forward." He's actually just a non-stop advice giver. His way of giving advice is often subtle, though. He doesn't lecture. He merely states his opinion.
Although he seems to keep himself from becoming too emotionally involved in the lives of the people he encounters, it is clear that he at least cares for them and wants what is best. He will often return to visit, usually a year later, to see how the people in question are doing.
In one episode, a man was willing to allow himself to be killed by a mushi for the sake of the rest of the village.
"The villagers love you! There has to be another way!" was Ginko's protest.
In the end, the man dies. Later, Ginko is seen playing back that moment in his mind. "Nope. Unfortunately not," he offers in response to his own earlier protests. "What an incredible thing to know a person's spirit," he reflects. Then, without anger or resentment, he looks upward toward the beautiful, now murderous, animal-like spirit resting on top of the mountain. "Right, Kuchinawa?" It's then time to move on to some place new. As Kurt Vonnegut would say: "So it goes."
Although he tries to do what he thinks is best, he is sometimes doubtful of his own decisions. There are instances where he withholds information, thinking that it would be better that way, but it instead proves disastrous. He also doubts his decision to allow a "half-mushi" to become a full mushi, as he thinks it must be horrible to be trapped in that state for eternity, despite the fact that it was the wish of the individual in question.
His way of speaking is casual and informal and even sometimes a little bit rude. He is generally laid-back and accepting, though he'll sometimes casually express such elegant thoughts as, "Damn, that sucked." He's also a bit of a meddler, butting into other people's conversations when he thinks that a mushi might be involved.
Ulterior motives are not his thing. He is usually blunt, honest with the facts, and he helps people because it is the life he has made for himself as a mushishi; it's his job to cure or help those troubled by mushi.
Contrary to other mushishi, he doesn't seem to want to eradicate mushi from the world. Often, if it can be helped, he will find a way for both the person and the mushi to continue living. However, if it can't be helped, he doesn't he mind killing them. His view seems to be to accept that which nature has created and to try to live with it the best you can. In one episode, he even has a conversation with a mushi that has taken on human form:
"Why do you kill us?"
"Because you consume human children."
"It's not my fault."
"It's not my fault either, except we're stronger, so you're going to die, along with your seed."
Interestingly enough, the mushi manages to remain alive, although it is no longer a threat to the people it was residing with. Ginko even takes it with him, presumably to take it to somewhere it can live without harming others. "Why don't you kill us right now?" the mushi asks.
"Because you still have life," is his response.
In short, when dealing with mushi, he seems to follow Nui's advice, though he has no memory of her.
During one of his travels, he met a man who was forced to permanently reside in the mountains by himself. That man expressed jealousy for Ginko's nomadic lifestyle. Later, Ginko reveals that he too was a little jealous of the man. Despite this, I don't think that he has any desire to settle down. He knows that it is not possible, so I don't think he would allow such a desire to foster or dwell in his thoughts. Although he might be an essentially lonely person, he is not an emo kid who would angst and dwell. In fact, he probably wouldn't even admit it, ever, even in his own mind. Instead, I envision that his loneliness would take the form of a kind of solemnness and solitude that is always there, but never expressed.
In short: he's pretty zen. 8)
He's one of the few people with a "strange" or "bewitching" quality known as youshitsu. It means he can see mushi, where as most people cannot.
He's also damn smart, well studied in both mushi and ordinary plants and natural phenomena. His travels have also taught him more than a thing or two about how to deal with people. He's able to talk them down from nearly every kind of emotional height, and people seem to instinctively trust him.
Important relationships and connections.