Hey guys, sorry for the late reply, I've been making a lot of preparations and I'm happy to make some announcements:
1. I figured out the situation for the most part with the guitars. I've settled with giving them away to someone at my "home" airport. I'll try and find someone who will really put them to good use, someone who has interest to learn bass or guitar, and I'll make sure to let them know to pass on the guitar to someone else if they lose interest and stop using it. As long as it's not going to waste I'll be okay with it, even though I wish I could've lent the electric guitar to my friend as I promised.
2. I figured out the luggage situation and I'm happy to declare that I should be safely under the limit with the amount of luggage I have (sorry I worded it weird, you'll see why in a sec). I have a backpack and satchel thing or whatever, which both count as "personal items", a small duffel which counts as a "carry-on", and a big duffel (one full backpack inside it, 3 empty replacements inside it) and small suitcase which count as "checked bags". I'm still working on getting the batteries for my scale, but as far as I know they don't exceed any weight limits. Yes, you might be thinking "but it depends on the airline" which brings me to this ↓
3. I have successfully bought the plane ticket, a huge milestone and barrier crossing in this journey for me! Thanks to everyone for all the support so far! Here are the details to give a clear idea of what will take place:
- On August 29th, I will be at my "home" airport to board a JAL plane, which will take me to Haneda Airport (with one layover).
- The ticket is one-way, so you can assume I will be using the onwardticket.com method in order to ensure success with this ticket.
- The ticket comes with 2 checked bags and 1 carry-on, while personal items are of course, included as well.
- I will arrive at Haneda Airport in the afternoon of August 30th.
- I won't say the exact price for now, but I'd say I got a pretty good deal, for having the luggage space and getting to the closer airport ('ω').
I hope to discuss the rest of it soon if I can't figure it out within the next few days!
4. I successfully reserved the SAKURA HOUSE of my choosing! Luckily, even now, neither bed has been reserved in the room I wanted. I got lucky, although there is one thing I am... maybe 1% concerned about. The room was booked until the 30th, so I decided to book it for the 31st instead. I assume it won't be a problem if I arrive in Japan the day before, considering as a night person, I won't really be "living" in the room until the morning? I will probably have to drag some stuff around for the day but I think that's alright, the main concern for me is whether I'd be refused entry for having my reservation a "day" later than my arrival. Also, would SAKURA HOUSE give me access to the room as soon as 12 AM on August 31st if I pay early, or would it be when they open their office later that morning? These are definitely questions I should and will be asking them
Well, I did it guys

I made some progress and took a big step forward which showcases my dedication to making this happen. Now there's no turning back, as I've already put the money into it

I've replayed the events in my head almost a hundred times by now, so let's do this!!
I'm hoping that I didn't make decisions too early, but I think that I made the right choice to do it now. I guess I followed the gut instinct without even thinking about it, since I was going to wait longer. We'll see soon enough if nothing gets in my way now

Thank you everyone once again for all your support in getting me to this point!