Corrales gained a 8-5 lead, but Mitani then proceeded to go on a 13-4 run to take full control of the first game on Friday.
The Spaniard kept fighting and narrowed the gap to 19-17 but her comeback fell short when Mitani won the final two points of the first game, reports Efe news.
The second game was tightly contested until 15-13, but the Japanese world No. 25 then went on a 6-2 run to clinch the victory in 37 minutes.
Next up for Mitani in Saturdays semi-finals will be 33rd-ranked Scotswoman Kirsty Gilmour, who upset 13th-ranked Sayaka Takahashi of Japan (the No 2 seed) 21-16, 11-21, 21-15.
The other womens singles semi-final will be an all-Danish battle between 20th-ranked Mia Blichfeldt (the No 3 seed) and 26th-ranked Line Hojmark Kjaersfeldt (the No 7 seed).
In the final four of the mens singles, top-seeded Suppanyu Avihingsanon of Thailand (the world No 31) will take on fifth-seeded Yu Igarashi of Japan and eighth-seeded Toby Penty of England will square off against second-seeded Rasmus Gemke of Denmark (the world No 29).
The Barcelona Spain Masters is the seventh Super 300 event of the inaugural season of the BWF World Tour of badminton, which comprises most of the years biggest badminton tournaments.
Unlike Super 500, Super 750, Super 1000 events and the BWF World Championships, Super 300 events do not typically attract a large number of top-10 players.Read More