Age (at present/beginning of Sensui arc): 26 (Flashbacks are seen of him at ages 5 and 16.)
DOB (given that the Sensui arc takes place in 1994): 6/6/67 (hehe..."666" followed by a "7")
Height (approx.): 6' (give or take)
Hair: Black Eyes: Blue (yes, they're BLUE!)
Canonical Love Interest (if you can call him that, since their relationship isn't like, oh, Gravitation): Itsuki
And also that annoying question SPS gets asked CONSTANTLY: "Why is there a little dot on his forehead?" :: Answer: Ever seen a statue of the Buddha? Sensui and Itsuki combined have some aspects of these representations...Itsuki's posture in the boat and the bindi on Sensui's forehead^^. (Togashi. we love your symbolism.)
In the ten years he went missing from Reikai, Sensui mastered eight different forms of martial arts, including his trademark, the Resshuu-ken, which is essentially a style that is a.) heavy on the legs and b.) a way to turn an opponent's own offense against them.
Upon his return to the scene, Sensui has gathered Itsuki and five other human followers to aid in the completion of a tunnel between Makai and Ningenkai to let higher-class youkai into Ningenkai to destroy humanity...and here the arc begins.
There is one thing that comes first and foremost into consideration when analyzing Sensui's character. This is that his ideals and morals, no matter how twisted they may be, come before anyone or anything.
That said, Sensui appears to be a loner, very serious, even before his faith in humanity was destroyed. He doesn't appear to be interested in many things besides his Tantei work, and his line between good and evil is absolute, and doesn't allow for any exceptions. He is even like this in his plan to open the Makai gate, although his positions of "right" and "wrong" have switched 180 degrees.
He loathes humanity with all of his being after witnessing the events of the Black Chapter and the Black Black Club on the night he raided their villa. That being said, it is quite likely since women bear children and cause the cancer known as humanity to flourish, that Sensui hates women. (Ever notice that in an anime with a kickass old lady and a woman who rules 1/3 of Makai, and even has women involved with the tournaments, that one of the major groups of antagonists has no females for seemingly no good reason?)
Also, Sensui is very intelligent and is an excellent strategist. You see this a lot when he fights...Resshuu-ken is a "defense-as-offense" style, and also when his Minoru-persona is philosophizing on the end of the world and on the evils of humanity.
As befits a cult leader (because that's ultimately what he is by trying to bring about the apocalypse with loyal followers), Sensui is very charismatic and can draw people to do what he wishes of them depending on the circumstance. (Remember how he pulled in Seaman and Game Master?)
Lastly, he is very human in and of himself, and has quite a bit of self-loathing because of it (in Shinobu-persona, it seems). Therefore he is very much prone to the mistakes he criticizes ohters for, which was probably the draw to him for me- I like to study hypocrisy, especially hypocrisy associated with religion and philosophy.