This was repaying the favor by Emperor Kanmu who could not fully repay the favor to Ostugu's father, Momokawa and concurrently the placement which the Emperor Kanmu executed expecting the future of Otsugu's ability.
これは生前に十分報いる事の出来なかった桓武天皇から百川への恩返しであると同時に、緒嗣の才能に期待をかけた人事である。