Kadomaru Corner Cutter series are tools to cut the corner of papers to give that plump and round corner. You can choose from three types of roundness.
Sunstar Kadomaru Pro, Corner Cutter (S4765036)
1xNew Rounder Corner S M L 3/5/8mm 3 in 1 Cutter Laminating Pouch - 2-1/4 X 3-3/4-20 Pack Office Set - AliExpress
Japan Sunstar Stationery Corner Cutter Kadomaru PRO NEO White cute design
Kadomaru Pro 3way corner cutter unboxing and review! I love this thing!!!
Japan Sunstar Stationery Corner Cutter Kadomaru PRO NEO White cute design
Sunstar Stationery Corner Cutter Kadomaru PRO NEO White : Tools & Home Improvement
This corner punch can handle 3-5 sheets of paper of weight under 64g/m2, and allows you to choose among small sizes (3mm), medium sizes (5mm) and large sizes (8mm) of corner radiuses. This Pro Neo model requires half of the force to use compared to the original corner cutter. The punch also features a lock at the end of the devise so that the lever won't move when it's idle.
Sun-Star Corner Cutter Kadomaru Pro Neo (White)
Sunstar Kadomaru Pro, Corner Cutter (S4765036)
Sunstar Stationery Corner Cutter Kadomaru PRO NEO Black : Tools & Home Improvement
1xNew Rounder Corner S M L 3/5/8mm 3 in 1 Cutter Laminating Pouch - 2-1/4 X 3-3/4-20 Pack Office Set - AliExpress
Sunstar Kadomaru Pro, Corner Cutter (S4765036)