Daisuke

Jigen Daisuke's appearance
Height: Tall and thin, firm and athletic body.
Face: Serious, with marked features and a hard expression; almost always with a cigarette in his mouth.
Hat: His classic black fedora, which he rarely takes off (it's almost part of him).
Attire: Dark suit (usually black or dark blue), light shirt and tie.
Weapon: A Magnum revolver, which he handles with incredible precision.
General style: Elegant, understated, and mysterious; conveys danger and experience simply by appearing.

Jigen Daisuke's Personality
Cold and serious: Unlike Lupin, Jigen is more reserved and quiet.
Extremely loyal: Her loyalty to Lupin is absolute; she trusts him even in the worst situations.
Pragmatic: Thinks logically and directly; doesn't usually waste time with nonsense.
Expert and professional: He is a legendary shooter, calm under pressure and very strategic.
Protector: Although he doesn't show it much, he takes care of his companions, especially Lupin.
Dry humor: He sometimes makes sarcastic comments, short but very effective.
Tough past: He has a hardened attitude, like someone who has lived a lot and is not easily fooled.

In summary
Jigen is the perfect counterweight to Lupin: serious where Lupin is chaotic, quiet where Lupin is loud. Elegant, dangerous, and loyal to the end.

He is estimated to be between 30 and 40 years old.
being most accepted that he is in his thirties.
Because?
He is a contemporary of Lupin III (who is usually around 20–30 years old).
He has a lot of experience, a weathered air and a tough past, but he's not an old man.
Physically he is in top shape, fast and accurate, which fits with that age range.
🧥🔫 Conclusion:
Jigen is a young-mature adult, experienced, serious and dangerous… the typical man in his early thirties with a history behind him.