Nice so far. I like the PS1 style graphics. Reminds me of Brave Fencer Musashi which is an under-rated classic. The Hyperlight Drifter influence is noticeable and I think you're hitting all the right notes with it. It's inspired by, without coming off as a clone.
Gameplay is great so far.
I'm going to just summarize my Music and Sound related comments to: Relax your approach to sound.
Music: Let the songs play and don't change the song from screen to screen. Changing the song too often makes it feel like you're constantly changing direction as opposed to working towards a goal. Maybe with each new screen or step towards a goal you can add a layer of music giving the player a clue that they are getting closer. This is something that Disasterpeace did well with huge tracks like "The Gauntlet."
New Song = New Area = New Goal
The whole first area could be one song that changes when you get to the boss. That will get our attention. Exploration time is over... Time to fight!
The music sounds well done. Let us hear it before changing the track.
Sound/Music Production issues:
Some of the effects and musical interludes seem to end abruptly with a click/pop. Let the sound fully play out. It'll add to the size of your game, but it will sound a lot nicer. The clicks are happening because the sound is being cut off. Before ending the sound, do a quick fade out (50-100 ms). That should remove the clicks. But, overall, I'd just let the sounds play out longer, especially if they're reverberating/musical in nature.
I know it seems picky but it's something that I definitely notice and takes away from the overall quality of the game and it's an easy fix.
Let me bind the mouse controls to the keyboard as well. I don't have a middle mouse button on my laptop trackpad, so I wanted a keyboard key for lock on.
I know it's a pain in the butt to program in this control stuff in Unity, but it makes for such a great user experience.
Being able to move the camera is great, but take control sometimes to focus on puzzles, directions or interesting vistas. It'll help you get the player going in the right way, and allow NPCs to make directional suggestions ("You can go this way <pan camera to show that direction> or that way <pan camera to show that direction>") It'll make it more immersive and allow you to make trickier puzzles.