Unkai seems to be the most informal of the five brothers, saying "What's up?" to Tadase even though he had only just met him. He looks to be quite lazy, as he was not dressed up for when there was a guest at his house. It is also possible that Unkai is interested in Kukai's love life, which is pointed out when he asked why Kukai didn't bring any girls with him.
Unkai has light orange hair which is half tied up, and half let down. He has brown eyes, and is quite tall. He has the same light tan skin tone as Kaidou, but he is much slimmer than him.
- Grandfather Souma: The brothers have a grandfather living in a temple on the mountains.
- Kaidou Souma: Unkai's older brother, and also the eldest brother of the family.
- Shuusui Souma: Unkai's older brother, and also the 2nd eldest brother of the family.
- Rento Souma: Unkai's younger brother, and also the 2nd youngest of the family.
- Kukai Souma: Unkai's younger brother, and also the youngest of the family.
- His first name has the same kanji that means "sea" like Kukai and Kaidou, and can mean "sea of clouds", describing his laid-back personality.