At first glance, he appears “cold and apathetic,” but his true nature—“extremely warm-hearted and highly professional”—creates a charming contrast (a tsundere‑kuudere) that is his greatest appeal. Here’s a summary of his main personality traits: 9 Cart Kramer
Main personality traits: Always in a low‑key, lethargic mood; basically always sleepy and rather lazy.
As someone who prefers to conserve energy and move as little as possible, he speaks very little and can come across as cold at first. A thorough realist: Because his partner Max tends to be idealistic and prone to rushing headlong into things, Cart consistently serves as the level‑headed brake (and straight‑to‑the‑point critic), calmly analyzing the situation. He excels at weighing pros and cons and managing risks. In fact, he’s incredibly warm‑hearted (tsundere): despite often making excuses like “It’s just business” or “I have no choice,” he simply can’t stand by when others are in trouble. Especially toward his partner Max, though he may grumble under his breath, he relies on him completely and will risk his life to save him in a pinch. Cold‑blooded yet professional when it comes to work: Once combat or a mission begins, he leverages his advanced cyborg abilities to carry out his duties with ruthless efficiency and no mercy. He’s a true professional who makes the optimal move without letting personal feelings get in the way. Clumsy and unable to be straightforward: He struggles to express his true feelings or affection directly. When thanked or shown appreciation, he’ll turn away and try to brush it off—a somewhat childish side (with an Earth age of 18,
a face quite fitting for his age).
…
And he’s a bit of a pervert, too—especially vulnerable to being thanked.

He’s a lovable but clumsy fellow, well-meaning and with a strong need for approval. As the official character description states, his guiding principle is simply the pure desire to hear someone say “thank you.” Here’s a summary of his main personality traits: ※
Max’s Key Personality Traits
Well-meaning and easygoing—mostly laid-back, yet deeply kind-hearted. Though he works in a legally gray‑area defense service, he can’t quite bring himself to be truly evil, and that very softness is his greatest charm. A strong need for approval—he longs to be thanked.
More than Cart, Max has an intense yearning to be appreciated and acknowledged by others; he tends to act in order to elicit a “thank you” from someone. Beneath his languid demeanor lies a warm heart—this is reflected even in the official fragrance and merchandise descriptions, which describe him as having “an awkward side hidden behind a lighthearted attitude” and as “seemingly aloof on the surface, yet harboring a gentle warmth within.” At first glance, he may appear like a typical, jaded modern youth, but deep down, he’s profoundly human. Absolute trust and reliance on Cart—though they often bicker, Max places complete faith in his partner, Cart. It’s precisely because Cart serves as a calm, level-headed straight man (the one who plays the tsukkomi) that Max is able to maintain his own carefree spirit and laid-back nature, making them an exquisite duo.