Hmm, i thought that both Ranma and Ryoga knew the attack. Only Ranma created
the Mokou Takabisha because he knew there was no way in hell he could match
Ryoga's level of depression.

And isn't the ShiShiHoKodan of 2 types? The one that Ryoga normally uses (ie
the energy beam shot) was the Incomplete ShiShiHoKodan. The completed
version (if i remember correctly) was the one where he releases a massive
pillar of energy into the air which then falls about him like a breaking wave.
      K  u  s  a  n  a  g  i       K y o
      --|---|--    --|---|--     ----+----
       +-----+     /-, +-+-       +-----+
       |-----|      |  |-|-       |     |      
       +-----+     -|- |-|-       +-----+
      ----|----    / \ +-+-       /  J  \
 -----------------------------------------------
  "Kusanagi Flames, Yagami Tears, Orochi Blood"