The only thing stopping him from soloing the game is the fact that he can't attack adjacent enemies without a specialized Bow/Yumi (which often has drawbacks like lower Attack Speed or Avoid), or the DLC skill Point Blank.
He also joins on a very shuriken-heavy map ( which are weak to bows), and the next map after that, all the enemies are fliers, which are more prime targets for his arrows. He joins very early with his special Fujin Yumi that is more powerful than anything you get for five or six more chapters. Takumi is very good to use in the Birthright path.
