This is by the creator of Astro Boy?
I read that later in life, Tezuka wanted to do something with a more adult theme than the work he was best known for. "More adult" in this case does not mean more emotionally or morally complex. It is simply outrageous, blissfully disdainful of credibility, and full of sex -- hetero-, homo-, and bestial. It is also over 500 pages long, but I suppose all those manga that come in installments are this long or longer. Still it is an intimidating tome.
Michio Yuki is a ten-year-old kidnap victim held prisoner in a cave on a Japanese island. He and his teenage captor make love that one night together. ("You're as pretty as a girl," the older boy keeps saying.) The next morning, everyone on the island is dead, due to the leak of a poison gas, the titular MW, stored there by Country X. (Now who could that be?) Yuki and his captor/boyfriend have escaped because of the altitude of their cave hideout. But tiny Yuki. it turns out, is short enough to inhale enough of the residual gas to lose any sense of morality.
Jump twenty or so years forward. Yuki is a strikingly handsome assistant bank manager by day and notoriously violent kidnapper on his off hours. His childhood captor, sorry I forget his original name and don't have the book in front of me, has become a Catholic priest named Father Garais. Yuki, knowing that what is said in the confessional cannot be repeated, confesses on a regular basis to Father Garais, They also have frequent sexual liaisons. Father Garais suffers spiritually but never turns down a roll in the hay with the still quite fetching Yuki. Yuki can also pose as a woman -- his family has a history of playing female roles in the Kabuki theater -- and seduces and murders his way to the top of the banking and political machine of modern Tokyo. His plan all along is to discover where the MW gas has been relocated and use it to destroy all life on earth. He is slowing dying from the low level MW contact he had years before, and wants to take the whole world with him. This kid wrote the book on nihilism.
MW is an entertaining farrago of sex and violence. Having it all in one, chunky volume made me feel like I was reading the worst, or maybe the best, Harold Robbins novel ever written.