This is a drawing of Ruby and Granite cosplaying as Toriel and Asgore respectively.
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Here, while they're cosplaying as Toriel and Asgore, Granite thinks that Ruby looks pretty in that Toriel outfit, but Ruby is very angry at Granite because she wants to enjoy her Toriel cosplay in peace without him falling in love with her. And that's pretty much all.
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Ruby and Granite© Jewelpet© Sanrio, SEGA Toys
Toriel and Asgore© Undertale© Toby Fox