Kansai RubyKaigi 09 and back to Hakodate

Kansai RubyKaigi 09 and back to Hakodate

Event and my presentation

My presentation on stage looked like this:

Photo by なかにしゆう

The event was at the Otsu Traditional Performing Arts Center. I got to do my presentation on such an amazing stage!

My presentation was about running mruby bytecode on Sega Master System, and its challenges. I used Claude Code to generate an AOT compiler for mruby bytecode. The AOT binary was a lot faster than running the bytecode.

Z80 at 3.58MHz is slow, and we can optimise a lot of stuff by pre-computing them. When you start optimising that way, it costs some space (think of pre-computed random number table as opposed to actually generating random numbers). When you pre-compute your bytecode execution, it is AOT compilation.

I think it was well-received, and I really enjoyed presenting it.

The presentaiton material and demos are here:

https://codeberg.org/yujiyokoo/mrubyz/releases/tag/2026-07-18-kansai-rubykaigi-09

Related events

I went to the beer bash on the night before at craft beer house B.B. The beers felt they were priced a bit high but they were very good. Afterwards, some of us went to Cosi Cosi, and there were people from the other party.

The official party after the event was at The Calendar, which was where I was staying at. After that, some of us went back to Cosi Cosi.

Otsu

On Sunday the 19th, following the event, I did some sightseeing around Otsu. I also went to Hikone to see the Hikone Castle.

It was great but it was such a hot day that I was really exhausted by the time I got there.

Late that day, I found a nice bar called “Bar Star” in Otsu.

Hakodate

I went back to Hakodate on Monday the 20th, and stayed there till Sunday. It’s an amazing city. One of the reasons I went back so soon was that I wanted to go somewhere I already knew, and Hakodate was such a place for me, as well as it was a lot cooler than most of the rest of Japan. I considered Fukuoka, but it was going to be too hot. I’d like to revisit Fukuoka when it’s a bit cooler.

I stayed at Hotel S-Pal. It was a little old but overall it was really nice and conveniently located. I’d stay there again.

Again, the food was amazing, and the people were very nice. I went to White Seed (both Suehirocho and Goryokaku) a few times. The beers were so nice.