The severity of the criminal charge (felony, misdemeanor, etc) depends on the specifics of the acts committed and the relative ages of the perpetrator and victim.
Missouri has ten statutory sexual abuse charges on the books which are used to prosecute age of consent and child abuse related crimes within the state.
One or more of these charges may be used to prosecute violations of the Missouri Age of Consent, as statutory rape or the Missouri equivalent of that charge.
The two participants in the relationship will reach an agreement about what each expects from the relationship.
Another major concern is that one of the partners will develop romantic feelings for the other.
Casual relationships, being a mix between a friendship and a non-romantic sexual relationship, result in the partners facing many challenges in maintaining a working relationship.