I'm not familliar with this game. The only thing comes into my mind is that you may plan for items in advance so that you can get most of them from enemies along the way rather than farm from the same type of the enemies that you just sneaked past, which you must have already been aware of since it's evident.
Farming items can be minimized because the only ones I can see ever really needing would be weapons, specifically rare drops. If I can manipulate a rare drop hammer or spear it would probably save the time forging (which I might end up having to do at some point anyway). I planned on farming an enemy along the way, the problem is finding one that isn't in a room with a bunch of others. I might experiment with a couple traps and see if I can get drops off of the monsters in them without losing too much time. So far I haven't been able to tell if drops are determined by X-Y co-ordinates, frame number or what.
I think i've used fruit like 3 times so far, maybe, and I'm pretty sure they were the ones you start with, so i think rare weapon drops will be all I'll need to worry about. I'm hoping I can find the calculations in the memory that decides how much str attributes and damage on your weapon needs to be done to do more than 1 damage as that would help my planning. In the meantime I'll probably just go to each boss and up my damage one point at a time to see. :/
Also, having the solar gauge up makes fruit (and probably other replenishing items) rot, and if you eat rotten items you get a 5 health gain, but it also makes the screen pixelate. I did it once in the run, but I might just optimize the damage I took earlier and my solar gauge use because it was actually kind of annoying to watch the game and not be able to see anything.
I'd like to see the next couple of levels. The bit you have done in that file wasn't boring, but it wasn't really enough to tell if I'd want to see the rest of the game. I played it for a few minutes after the movie ended and thought it might be sort of entertaining to see the next few levels optimized.
I recently decided to pick up TASing on a whim, and Boktai 2 was one of the first games I considered as it's a personal favorite. The main problem with TASing Boktai is that it's very puzzle and stealth heavy, so there isn't any reason to fight monsters except for during Traps and farming items. Compounded on that, I've not yet found any sequence breaking opportunities or means of making rooms/dungeons faster other than perfecting paths. It makes me think most people probably wouldn't find it a very entertaining run, unless perhaps you like the game as I do. Maybe not though, it's an awful lot like MGS in some respects, and the TAS of that that's being worked on is reasonably entertaining. There's also a whole lot of talking sequences that seem to be unavoidable (though some of them I've found are), which can also be a deterrent to watching.
There isn't a lot that I've found in the way of speed saving so far; staircases and ramps are coded in such a way that you can walk onto them several pixels above their lowest point, you can speed up fights by standing parallel to a monster and facing a certain way to hit behind them, which in some cases means you don't have to move to far in one direction to optimize damage done, and . One thing I've had in mind since I started that could eventually lead to a problem is that the solar patch version I'm using has the solar bar set to L, which could possibly get in the way later in the game when I acquire dash. The alternative patch uses select, I believe, and that would mean only being able to turn the solar gauge up when changing weapons/magic.
I've hit a roadblock with the WIP on Durathror and need to go back in the run and find a monster that I can manipulate into dropping a stronger weapon and possibly level up once or twice, so I'm in the process of cutting the run up room by room and optimizing each one as I re-record from the old file. I should have a newer WIP sometime soon, I've so far saved about 2000 frames on my old one.
It's too bad there wasn't already a topic for this game, or even the first one. The most I could find about either was 5 minutes of a TAS on youtube and an unoptimized example run of Boktai1 somewhere on these forums. :/