You can get one Angel Beats! character right away

Maybe now is the time if you're starting new? I chose Yui on an account that was doing self-invites. Is Yui the safe choice if your goal is to clear Chapter 2-10? However, they give out a 10-pull ticket, so you should probably pull first and then choose a character you didn't get (I got Iwasawa with the 10-pull ticket, so I chose Yui). And personally, good news! Please tap the right side of the home screen. Even if you haven't unlocked it with a key, you can listen to that song you heard in battle in its entirety on this screen! However, it seems like new players need to clear Chapter 1 first. For your reference, the Heaven Burns Red versions of Angel Beats!'s Crow Song and Alchemy can be heard even at this early stage when you've just started and haven't cleared anything yet. It's just that it takes a bit long to get to the home screen when you're just starting. As a side note, I recommend using the subscription service to listen to the songs without having to download the game. I thought 'After You Sleep' wasn't on the album and I wasn't familiar with it, but it seems it was on the Heaven Burns Red soundtrack. I was momentarily worried because I hadn't cleared the previous event which I thought had already passed its deadline, but the deadline is actually still okay, so I cleared it just in case I forgot.