Beyond any doubt, my proudest technical achievement would be my work on Ys I & II. It'd be easy to say Corpse Party, but while that's something that was achieved and that I'm proud of, it feels less rewarding in some ways.
Ys I & II required working with multiple versions of the same game's source code, dealing with really ancient graphics features (256-color palette limit on screen at any time, etc)...
The big things with that game are that I had to implement a screen mode and features from another, much older version of the game because the PSP version's display was so zoomed in as to make it less than optimal. And this involved huge amounts of work you might not have thought a lot about.


For instance, not only did I have to use code and data from the old version of the game to restore the gist of this functionality, but I also had to obtain the original assets for the PSP-exclusive art mode. I then had to use those to make new crops for the larger viewing size, because the PSP version hadn't accounted for the idea that it would ever be backported like that. But now you can see even more of those images than you could on PSP!
This also had its own unforeseen consequences, because I had to create new palettes for these versions of the portraits and implement those into the game, which created problems here and there that I had to fix. Similar issues would arise from implementing the two different colored frames that can be used in the Eternal/Complete style view mode, and when implementing full mouse support for the games later on.
In general, while I feel like Corpse Party may have been a bigger accomplishment in many ways, it's something I look back on less fondly overall. My work on Ys I & II is something I can look at and immediately feel very proud of, preserving a game that's so historically important and bringing the best of the different official versions available into one package.
Ys I & II Chronicles+, with an emphasis on the "plus", is something I can say is uniquely my accomplishment and that few people would deny is one of the best ways to experience two very classic parts of video game history. Those who would say it's not THE best are those who have nostalgia for the PCE/TurboGrafx version that originally hit the west back in the day, which definitely makes sense, since that version is, well, nostalgic! But even then, those people will typically say Chronicles+ is the second-best way.
It's also my work on Ys that really made me fall in love with Falcom games, something I am incredibly grateful for. I knew of them, I was excited to work on them in a general sense, but I had absolutely no experience with Falcom before working for XSEED, and quickly became a true fan with a strong love of Falcom's classic titles.
There's probably a lot more I could say here, frankly... but this is what I could think of when writing this post, so I hope it was a fulfilling answer.
