Heat oven to 425°F; oil a rimmed sheet. Mix panko and milk; gently fold in beef, pork, egg, ginger, garlic, salt, and pepper. Shape 24 meatballs; bake 16 to 20 minutes until centers reach 160°F.
Meanwhile, simmer pear, gochujang, soy sauce, vinegar, brown sugar, and broth in a saucepan 3 minutes, stirring until combined. Transfer hot sauce and meatballs to a 4-quart slow cooker.
Cover; cook on HIGH 2 hours, turning gently once. Whisk cornstarch with slurry water; fold into sauce. Cover; cook on HIGH 15 to 20 minutes until thickened and centers reach 165°F.
During final half hour, boil rice and rice water in a saucepan. Cover; reduce to low and cook 18 minutes. Rest off heat 10 minutes.
Turn off cooker; gently stir sesame oil through sauce. Divide rice among 6 bowls; add 4 meatballs and sauce to each.