5-Sided eraser (Mirikesi) by Kokuyo. The eraser comes with 5 different widths. The different widths are designed to erase small writing, especially in planner and notes. Sometimes, a standard eraser might accidentally erase multiple lines at the same time, but this is designed to erase precisely. The numbers on the eraser is the width (indicated on the side and also the ruler on the plastic cover). It goes from triangle (pointy with no width), 3mm, 4mm, 5mm to 6mm. The eraser erases nicely, and it's a convenient tool for students or anyone who takes lots of notes.
Kokuyo started in 1905. Their mission is to solve the small problems people encounter in their work and daily lives. Many products from them come with a small clever twist to improve an existing idea.