Soak ribs in a large bowl of water for 1 hour.

Meanwhile, combine Asian pear, onion, garlic, and ginger in a blender or food processor; puree until smooth. Transfer mixture to a mixing bowl. Add 3/4 cup soy sauce, rice wine, water, brown sugar, 1 tablespoon sesame oil, and pepper and mix to create the sauce.

Drain ribs and dry them well. Trim off excess fat. Place ribs in a multi-functional pressure cooker (such as Instant Pot®) and add carrots and radishes. Pour Asian pear sauce on top. Close and lock the lid. Select Meat function according to manufacturer's instructions; set timer for 35 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer's instructions, 10 to 40 minutes. Unlock and remove the lid. Transfer meat and vegetables to a plate and set aside.

Select the Saute function on your Instant Pot®. Stir in remaining soy sauce, remaining sesame oil, and white sugar. Cook, stirring occasionally, until sugar has melted and sauce has thickened, about 10 minutes. Return ribs and vegetables to the pot to get nice and saucy.

Garnish ribs and vegetables with green onions and sesame seeds.