You must make progress on Chains of Promathia missions until you flag The Road Forks to be able to do this mission. If you haven't started those missions yet, it will take approximately 4-5 hours depending on travel time.
Along with the roadblocks mentioned in the prior mission notes, anything that renders Prishe, Ulmia, and/or Tenzen unavailable will halt your progress. As such, once you get this cutscene, it is strongly recommended you finish up to a minimum of Desert Winds (no longer need Prishe) or, ideally, Both Paths Taken (no longer need Tenzen) before continuing Chains of Promathia.
If your inventory is full & you did not receive the Cipher of Tenzen's alter ego II, make a space in your inventory & check the Mystic Retriver at (H-7) of Ru'Lude Gardens.
Having heard about Tenzen, Iroha has headed toward Ru'Lude Gardens in Jeuno. However, she warns that you must pass the trials posed to you by the chains of Promatia to move forward. Perhaps a fateful meeting awaits you along the way.
SPOILER WARNING: Click here for additional details about this story line.