Is it legal to walk into a neighbors property and pleasure ones self to their daughter if she is unaware of the happening?

Call the cops and tell them what happened.

So you want to know if it's kosher to trespass on another person's property and publicly masturbate because you were peeping into your neighbor's window and _thought_ you saw your neighbor's daughter engaging in a sex act? A brief review of the Minnesota Statutes and case law does not uncover any "naked neighbor's daughter" exception to either Trespass or 5th Degree Criminal Sexual Conduct. It's not trespassing if you have the property owner's permission, so you might want to ask your neighbor if it's ok if you go onto his land and masturbate to his daughter through the window. If so, you're not trespassing.