Hey there, Youmitsumi! I took a gander at a few tracks on your profile, and I am glad I double-checked your post after listening! You said that you have grown interested in sound design, and my first comment was going to be about the ambiance you have in the first few tracks of your portfolio. I really like the way you combine the use of ambient textures to compliment your pieces. As a video-game composer (honestly, a composer for any type of media), I believe that writing music to compliment the environment it is being based in is an important skill to have!
Based on what I heard, you seem to naturally have a knack for ambient music (taking into contribute to your piece, Rain Forest, particularly). Although that is the first track, it is one that ultimately stands out the most to me. Plus, I kind of get an ethereal, translucent vibe from many of your pieces. Seashore reminds me, A LOT, of this particular track from FF X -
I think, if anything, I would say, for one, integrate more depth into your pieces. By depth, I think I mean bass, or low voices. Kind of work between different registers a bit more. Also, try to integrate a wider range of timbres and instruments into your works. In Dancing Blocks, your piece really opened up at 5.53 when you brought in the strings to break up the electronic tones, and I feel you could have achieved a deeper, fuller sound had you incorporated instruments/synthsizers on the low end to fill out the seemingly empty spaces. Also, try expanding on your musical ideas a little. Pieces like Seashore and Rain Forest do well as ambients, but you can also change tonal centers, add acoustic effects to help shape the background environment, etc. etc. Just thoughts.
Lastly, I'd like to second 10Ahead's note on the length of your demo reel. I've gathered intel from a lot of notable sources on the site and I'd have to agree with them when they state that demo reels need be short and sweet. Instead of including full length versions of your pieces, gather an assortment that showcase your versatility and skill as a composer, and trim/edit them accordingly. Many developers looking for composers spend time sorting through portfolios, and when you present a demo reel, your best bet is to get them engaged and interested as quickly as possible (like t.v. commercials). Me personally, I'd keep my demo reel between 3 - 5 minutes (though some would say shorter, and some longer). It is ultimately your preference, but 10 minutes is a bit lengthy, so obviously 19 is far too much time for one to take to generalize your capability as a writer (as shaddy and shallow as that sounds).
Anyway, I think that you are doing great. I'd love to hear more ambience from ya'!