Rider Skills: First off, you as a Monster Rider have a number of skills at your disposal and they each take a different amount of Kinship Gauge points to complete.This is the Kinship Gauge, and it can be used in a few different ways.
If you and/or your Monstie completes a successful Head-to-Head or Double Attack the gauge will fill a lot more. Each time you land successful attacks this gauge fills a little. You'll notice a circular gauge near the bottom of the screen that fills with blue light as you battle. Monster Hunter Stories 2 Joint Attack (Image credit: iMore)