((<Apache Arrow|URL:https://arrow.apache.org/>)) is the de fact standard data format in modern data processing systems. We can use the official ((<Red Arrow|URL:https://rubygems.org/gems/red-arrow>)) gem to process Apache Arrow data. It's suitable for fast large data processing but it's over-performance for only low cost data exchange needs. Red Arrow is larger and a bit difficult to install than pure Ruby gems because Red Arrow is implemented as bindings. I'm implementing the official pure Ruby Apache Arrow reader/writer for only low cost data exchange needs. I expect that more Ruby libraries and applications add support for Apache Arrow inputs/outputs by the pure Ruby Apache Arrow reader/writer. Ruby can be used more for data processing by it. This talk describes how to implement fast pure Ruby binary data reader/writer and the future of data processing in Ruby. This is a 2025 Ruby Association Grant project: ((<URL:https://www.ruby.or.jp/en/news/20251030>))