Minna no Ginko (Minna Bank) Style Design System (DESIGN.md, Japanese UI)

Design policy: A digital bank composed of only three colors: pure black, pure white, and fluorescent yellow. Rectangles are drawn with thick 2px black rules, and hand-drawn-style monochrome illustrations are placed on top - Density: Low. Based on a single-column 504px vertical scroll, bringing the smartphone app's flow directly to the Web - Keywords: Pure black / pure white, fluorescent yellow #eeff00, 2px borders, zero-radius rectangular buttons + pill stickers, no palt