Kalgan has dark hair and big, dark-colored eyes. As a young boy, he has a small stature and is often covered in small bruises. Coming from a poor family, he wears cheap clothing made from the Kai Empire.
Kalgan is a rather curious and sharp child, who is actually quite weak. He catches illnesses quickly though he doesn't say anything about it. This is likely why he was attracted to Yona (as she shot down a bird for him to eat, since he was hungry) and why he said he liked 'strong women'. However, he also seems to like caring and kind women, as shown when Yoon offered him food (he thought Yoon was female to this point).
He is a reckless child, and disobeys his father's orders to stop going to Kouka Kingdom. He seems to see through a lot of things, even deducing that Yona likes seeing Hak happy and may have possible feelings for him, whilst also becoming aware first that he may have been the one who shared the illness that Kija, Jae-Ha and Shin-Ah caught. Not only this, he also has a good idea of what is happening between Kouka and Kai, knowing that the villagers always seems to look across the river for a reason- even though his father has limited him to discovering issues such as the war between the two countries.
He has a rather odd image towards relationships and love, asking Yona and Yoon to marry him at their first meeting, without even knowing them properly and after they gave him food. He also labels a person quickly even if he knows nought about them from their actions, just like when Kija carried him on his back the immediately called him a 'nice person' and said that he would have 'run away' if he knew that there was such nice people living in Kouka.
Although Kalgan does not seem to possess any special abilities, he seems to have a very sharp mind. Just by looking at people's reactions, he can guess quite accurately what is happening in the scene.