Xeno is an adult man with white hair styled into a large pompadour that is slicked and spiky towards the back. He has thick eyebrows that widen at the arch and large, dark eyes with no visible irises and heavy bags underneath, making him look slightly raccoon-like. He has a small nose and small mouth with no visible lips. His most notable facial feature is his extremely prominent forehead and the huge petrification scars crossing it. The scars are in the shape of an 'X', ironically the first initial of his name. He is most often seen with a smug, confident grin on his face. Xeno is a scientist and worked for Nasa before being petrified. Similar to Senku, Xeno is brilliant when it comes to science. He likes to give lectures on the various scientific endeavors he is involved in. He is very observant, as he noted that Gen's group was skilled at facing the dangers of crossing the seas of the Stone World and that Gen may be lying to him after noticing he didn't fail his polygraph test. He is somewhat eccentric, as he would invade Gen's personal space while asking for his identity in a menacing manner. According to Luna, Xeno would often state the word "Elegant", when something amazes him. This allowed Senku to remember him.

Senku is a straightforward, confident, and logical individual, who is also aware of the limits of his abilities. His decisions are often backed up by his vast knowledge of science and applying the scientific method. Senku never belittles those who are less knowledgeable than him, however he does have a habit of diving into complicated explanations in an attempt to teach others. However, his enthusiasm for science encourages and inspires everyone around him to do better. Because of his charisma and caring nature, people tend to gather around him, allies and enemies alike. Senku is also able to admit his mistakes, for example if he misses important information, such as when Kohaku pointed out that the north star did not align with north as he claimed, since Senku had overlooked the Earth's precession. Senku is a scrawny and physically weak young man of average height with pale skin. He has white hair that fades to green towards the ends, spiking up naturally into soft tips. Two locks of hair drape over his face. He has sharp red eyes, slim eyebrows, a small nose, and a mouth that tends to curl into an evil grin. He has two symmetrical petrification scars on his face, jagged lines beginning from his inner eyebrows and heading towards his hairline. On occasion, smaller scars leading down from his inner eye are visible as well.