A dosu is a gigantic yukkuri (size varies but are usually equal or bigger than an adult human) that mainly exists in the wild. Dosus aren't a separate species, rather a normal yukkuri has a chance to grow into a dosu though the conditions and causes of dosu transformation is unclear.
Normally recognizable due to their gigantic sizes, either in general or to other yukkuris, dosuyukkuri (dosus) are typically the bosses or chieftains of a yukkuri clan. Yukkuris who are long-lived and/or especially easy may grow to become dosus, although Marisa is by far the most common type of dosu. Trained dosus may be used by humans to regulate artificial clans.
Dosus are often depicted as having one or more superpowers. The most common power is "dosu spark", a laser attack similar to the real Marisa's Master Spark. Sometimes, this attack is performed by eating "dosu mushrooms" that they can locate or grow. Other superpowers varies from stories but some of the more common ones include causing plant life to spontaneously grow near them (thus making nearby yukkuri populations prosperous), causing nearby yukkuris or even humans to feel easiness just by being nearby, or turning invisible against uneasy yukkuris or humans.
The strength of a Dosu varies from each story. Some stories depict Dosus as extremely powerful and dangerous (particularly their dosu spark) and often humans require special procedures and a full team of specialists to kill a problematic dosu. Other stories depict Dosus as powerful but a single human is still more than capable of defeating it alone. And some stories depict dosus as nothing more than an oversized yukkuri and is just as easy to defeat as normal-sized yukkuris.
Dosus tend to be niceheads that is friendly to any yukkuri and even humans. But shithead dosus does exist and these tend to rally up fellow shitheads to invade human farms and houses thanks to their above-average strength and dosu spark ability. This tend to not end well for the dosu as as mentioned above, humans have developed anti-dosu procedures and is generally accustomed to dispatching problematic dosus. Often times a farmer is shown to have above-average combat skills and can easily defeat a dosu in a fight.
While shithead dosus are universally disliked as any shithead, the relationship between nicehead dosus and humans varies between stories. Some humans see dosus in a good light, they make the wilderness more bountiful (thus wild yukkuris shouldn't need to invade human farms) and these dosus are niceheads anyways. Other see them in a more negative light as dosus makes yukkuri communities more prosperous and can risk a yukkuri overpopulation which will can cause trouble for humans farms anyways. These farmers thus will gather and kill a dosu if sighted regardless if the dosu is a nicehead or not.
Dosus are mainly wild yukkuri and is almost never seen in the city as there is no room for a yukkuri to grow into a dosu in the city. Rare cases of gutter trash yukkuris does exist though these dosus generally have adapted to the stricter living spaces in the city and thus are significantly smaller than wild dosus (though they're still bigger than a normal yukkuri). It's unclear if city dosus have the same superpowers as wild as they're rarely sighted and can be hard to distinguish from just regular big yukkuris.
While rare, bodied yukkuri dosus are known to exist.