Men are polygamists by nature. Islam being a religion of nature, has allowed men to have multiple partners. That too, in a temporary Or permanent marriage. Islam has given a sizeable margin of freedom in this area, for obvious reasons. However, culturally it’s not allowed. Culture restricts men to have one committed relationship throughout his life. If your (that guy’s) urges are too hard to control and pushing you towards sin (self-pleasing is also haram btw), then go ahead and do it the Halal way, and don’t feel guilty about it. When you make God incharge of your affairs, then you don’t have to worry about the consequences. However, make sure you refrain from cheating, lying and deceiving in all your actions/decisions.