I have a 19 year old friend who is currently dating a 15 year old female. I was wondering if this was legal or not? If not what legal recourse would he be facing? He is also turning 20 this year and she will be turning 16. Does this make any difference?

If the 19 year old is sexually involved with the 15 year old, he is in violation of the Ohio Statute below and can be charged with a felony of the 4th degree or a misdemeanor of the first degree there is less than 4 years between them in age. This would depend on the month their birthdays fall within the year.

§ 2907.04. Unlawful sexual conduct with minor.

(A) No person who is eighteen years of age or older shall engage in sexual conduct with another, who is not the spouse of the offender, when the offender knows the other person is thirteen years of age or older but less than sixteen years of age, or the offender is reckless in that regard.
(B) Whoever violates this section is guilty of unlawful sexual conduct with a minor.
(1) Except as otherwise provided in divisions (B)(2), (3), and (4) of this section, unlawful sexual conduct with a minor is a felony of the fourth degree.

(2) Except as otherwise provided in division (B)(4) of this section, if the offender is less than four years older than the other person, unlawful sexual conduct with a minor is a misdemeanor of the first degree.

(3) Except as otherwise provided in division (B)(4) of this section, if the offender is ten or more years older than the other person, unlawful sexual conduct with a minor is a felony of the third degree.

(4) If the offender previously has been convicted of or pleaded guilty to a violation of section 2907.02, 2907.03, or 2907.04 of the Revised Code or a violation of former section 2907.12 of the Revised Code, unlawful sexual conduct with a minor is a felony of the second degree.