Yukio Seki, linked below is the pilot who might had plunged into St. Lo:
WW2DB: Yukio Seki
Now, note I used the word "might" -- I don't believe it had been proven that the explosion on St. Lo was the result of a kamikaze attempt. While Seki's aircraft was probably the one that caused the explosion, there are still some argument on whether the explosion was caused by a bomb he released before crashing, or if the explosion was the result of a deliberate suicide plunge.