Like a Dragon: Infinite Wealth

You can either level up a Sujimon by feeding them an enhancement item (Sujimunch) via the 'Strengthen Sujimon' menu at a Suji Spot (these are all over Hawaii, though not marked on your map) or through sparring and competition. Suji Spots glow green, and walking up to them will grant a free item for your Sujimon. You can then interact with the yellow console and Awaken and Evolve your Sujimon, too. To praise a Sujimon and level up your friendship with them, you'll need to head to your farm on Dondoko Island. The farm is unlocked part-way into the Dondoko Island substory, then you can put Sujimon to work harvesting vegetables, gathering materials, training, and more. To raise your friendship level, interact with a Sujimon (a 'Praise' prompt will appear), then waggle the analogue stick (or your finger on the touchpad) to 'pet' them and show your appreciation. In the top right corner during this, you'll see a heart icon fill up. Once this is filled, your friendship level will be maxed. The best way to knock this one out is to concentrate on a single Sujimon to lavish your attention upon.