Dokuga often seems cold on the outside but is very warm on the inside. He usually wears an emotionless expression, sometimes with hints of weariness or sadness, but he has good reasons for being the way he is.
His poison saliva has far-reaching consequences in his personal life, and probably shapes his identity more than anything else. It doesn't discriminate between friend and foe, making him a walking biohazard. It isolates him even among his comrades: he eats alone, bathes alone, sleeps alone, and has his own special utensils. If he has to engage in a communal activity that exposes others to risk of his poison, he does the activity last (and alone).

This is more than simple inconvenience. It's a fundamental sense of separation that pervades his entire experience of the world. He says he's "just living life in a way that doesn't cause trouble for everyone," but what he really means is that he is trouble. He is poisonous. Just by existing, he is a danger to everyone around him.

And this doesn't only affect purely superficial routines, but his outward emotional expression. He has to reign in the natural physical impulses that come with anger and joy. As Natsuki pointed out, he can't even kiss or be intimate with someone, which severely restricts his freedom in interpersonal relationships.

This results in a false external calm when, in fact, his internal emotional world has not dulled one bit. Instead of making him more neutral, it could be said that the physical repression actually amplifies his feelings. So overwhelming are they that, when convinced to outwardly share them, he literally doubles over and has to support himself against walls.
The sense of isolation is compounded by the fact that the whole sorcerer world treats him, and others like him, as an outsider. Because he can't emit magical smoke, society has drilled into him since childhood that he's nothing, that he's nobody, that he's trash. So abysmal was his self-esteem as a kid that he welcomed rain-induced agony as justifying his existence.
Maybe his childhood could go towards explaining his genuine humility.

He really has no pride to speak of, and downplays compliments offered him by Natsuki. Whether it was a matter of politeness, a realistic assessment of his abilities, or his own opinion of himself, it says something about his character.

Another interesting indicator was the cross-dressing episode. There was no flaunting, no complaining; didn't even tell anyone. He just surmised that he could pass for a hot girl and did what had to be done to save his friends.
Not that good
Here the CrossEyes Officers are investigating where Natsuki suddenly disappeared to. Dokuga leans in, and then... wait for it...
Naked Natsuki pops out. Dokuga does a panicked blush. The next panel he's gone, replaced by Tetsujo, while Ton is unfazed.
It's important to note that he wasn't blushing because he saw an arguably attractive young girl naked. Dokuga is just an acutely self-conscious person and was blushing from the awkwardness of the situation.

He was blushing even harder all through the scene of having to undress the dead and relatively unattractive landlady. Even before the bra came off, he was blushing and sweat-dropping at the thought alone.
Perhaps this intense awareness of his surroundings is also what makes Dokuga so considerate of others.
He not only packs Kai's lunch, but has the foresight to put together an emergency survival pouch that ends up saving his life.

And speaking of pouches, the bags he wears tied to himself look an awful lot like black powder pouches. This gave me the mental image of Dokuga as some black powder pixie that runs up to sprinkle some on Kai if he runs out of smoke. Of course, we now know he keeps all sorts of fun things in there!

After Kai turned into a monster with the mind of an autistic child, Dokuga revealed his maternal instinct and skill as a babysitter.
I'd like to point out that Dokuga is not sexist.

When his beloved Boss is transformed into a pie and Kirion kicks the pie out a window, Dokuga is furious. Yet, despite this, he remains polite enough to not bring gender into it.

Though what he calls her can accurately be translated as "you bitch," what he actually says is "kisama." It is a derogatory word, but nevertheless gender-neutral.

This is in contrast with other characters (notably Fujita and Chota) who I have seen use the gender specific derogatory "kono ama" (notably towards Nikaido).

These little things matter to me...
Not Sexist
Dokuga is also highly resistant to interrogation and torture. Aside from his obvious loyalty to his Boss, his childhood likely acclimated him to abuse. He'll writhe and scream, and show every sign of fear but he'll never talk, even if you feed him alive to flesh-eating worms. When Chota kept calling him "trash," a word used to oppress him all his life, Dokuga did not fight it, for he has little use for pride or self-preservation.

Both Shin and Shou recognized this quality in Dokuga, which I see as a sign of their respect for him (mixed with annoyance). And truly, Dokuga had never been in such a blatantly hostile situation before. Sure he's had a very rough life, but he always had his friends by his side. Now he was utterly helpless and alone in a den of elite magic users, deprived of all hope because he knew his Boss couldn't back him. And, despite his growing doubts about Kai's motives, Dokuga still didn't talk to the enemy.

<<< More Than Just a Prettyboy HOME Dokuga's Fighting Style >>>
DISCLAIMER: all story, art, characters are copyright Q Hayashida. This is a fansite. No copyright infringement is intended. Translations by Gantz Waiting Room, VIZ Media, and sometimes myself. Dorohedoro is published in Ikki Magazine.