Valentine Envelope Valentine Envelope – Sumiko Momotani. Made from a square sheet of paper. Flap slotted into aperture. Adapted from a fold attributed to Sumiko Momotani (referenced in British Origami Society Magazine, 128) and Y. and S. Momotani, Image and Expression. See also Hawk Envelope. and Bunny Envelope, Yoshihide and Sumiko Momotani, Origami Kawaii, (ELFA library).