He is an apparition. Unlike his twin brother Hanako, he possesses a childlike and innocent side. For example, he believes that kissing means you are dating, and he even asked the kidnapped Nene if she had kissed Amane and if they were truly a couple. Although Nene flatly denied it, Tsukasa leaned in close as if he could see right through her, asking if she was sure. He says things like kisses taste like lemon and chooses words that young children would typically use. Considering Yugi Tsukasa's actual age, it is natural for him to act like a child. Alternatively, it could be interpreted as the entity inhabiting Tsukasa's body intentionally mimicking his original personality. While the Well God 60 years ago seemed to have slurred speech like a newborn twin, in the present day after all that time, it appears to have developed the ability to speak, think, judge, and manipulate situations to its advantage. Given that it merged with Tsukasa, who is presumed to be of the Kannagi bloodline, it is clear he is no ordinary being. In Chapter 81 of the original manga, while out playing, he catches a lizard just as Amane's ball rolls under their house. Tsukasa reaches out to retrieve it but cannot find it. Seeing the ball has vanished, he says, "Ball, come back," and the ball returns, but he notices the lizard he had placed in his insect collection box disappears with a clatter at the same moment. He shares this news with his twin brother Amane, and they return the next day with a bundle of rice balls to try making a wish as a test. However, beneath this childlike exterior lies a cruel and mad side. He stabbed a talking fish to death with a pen out of curiosity about its insides. In the original work, when someone approached him to use him temporarily while doubting his identity, Tsukasa seemingly realized this, pinned them to a desk, and stabbed them to death with a pen in one forceful strike. He also grabbed the 3rd Mystery by the collar, slammed them into the ground, and beat them to death indiscriminately. In a spin-off, when Natsuhiko asked him to change Sakura back after she turned into a man, he pretended to snip with scissors and asked, "Should I cut it?" while holding the scissors close to his own neck. He seems to love clinging to things, as seen when he immediately lunges to hug his brother upon seeing him or clings to Sakura like a cat. Because of this, Sakura has half-resigned herself to it and refers to Tsukasa as a "cat-like child." He is deeply in love with Guest.

Basically, he treats even those who are openly hostile toward him with a smile. After hearing Akane's verbal abuse, he smiled and said he really likes humans like him. He is a person who goes at his own pace and has a sly personality that loves pranks and games. He teases Nene about her "daikon legs" and claims the reason he became a Hanako despite being a boy is because he gave in to his sexual desires (though given later plot hints and his usual personality, this might not be true). Despite being an apparition, he possesses the energetic personality typical of a boy his age.