The Sugai series of math courses offered during Sundai's seasonal lectures. This course is taught by Mr. Sugiyama, a member of the Sundai Kansai Math Four Heavenly Kings, who has helped students pass both the University of Tokyo and Kyoto University, and is the author of "Complete Mastery of High-Level Mathematics." The text focuses on learning typical mathematical techniques, and the difficulty level is slightly easier than "One-to-One Correspondence Exercises" (though this might just be because Mr. Sugiyama is a good teacher). This course is worth 260,000 yen. All the notes are written in the text, so you can study independently like you would with a commercially available reference book. I personally found this text very helpful. If you are seriously considering purchasing it, I am open to price negotiations, so please feel free to ask!