Flow can refer to two things (having a double meaning):
1. Ryuto's ability to feel his opponent's flow or rhythm.
2. Ryuto's ability to get in the mind state that is known as "Flow" in psychology a.k.a "Access Concentration" in Buddhism. Flow is state of mind where one is fully absorbed and immersed in the activity at hand. When one is in flow one obtains high levels of focus and concentration.
Ryuto's main talents is in his aptitude regarding these two skills