A yukkuri poses with a slightly upward gaze and eyes sparkling as if viewing a glorious future, its cheeks swelled and an expression of determination on its face. The mouth is in a closed-lipped smile, while the eyebrows are angled downwards like a frown. Often accompanied by a *shine* or キリ sound effect.
Often interchangable with smug, with the only difference is 'proud' doesn't always connotate arrogance while smug always does. Honestly the two tags can probably be merged.