Rising Japanese star Kaoru Mitoma struck a hat-trick after coming off the bench in the second half on Saturday, sparking Royale Union Saint-Gilloise to a 4-2 comeback win over Belgian top-flight opponents RFC Seraing. Entering after the break with Union trailing 2-0, Mitoma quickly helped the home side shift the momentum at Brussels’ Stade Joseph Marien. He put Union on the board in the 55th minute with his first Belgian league goal, receiving a through ball at the left of the area and finishing from a tight angle across Seraing keeper Guillaume Dietsch. With Union level from an equalizer by w…