These past few years, I have been working on a yet another Ruby implementation named "monoruby". Monoruby is written in Rust, consists of a parser, garbage collector, bytecode-based interpreter, and just-in-time compiler. All of these components were built from scratch. This is not just a toy project; we ran the Optcarrot benchmark on monoruby and its performance was comparable to other modern and fast Ruby implementations such as YJIT and TruffleRuby. In this talk, I would like to present the design and implementation details of monoruby.