Hello hello

Well, I think that as Yumi knows really well Kan-chan he knew he would still have those photos from the past and I think it was just his way (Yumi's way) to tell Kan-chan that it was okay to let it go. So, in order to let it go Yumi gave the album to "store" the past in a safe place.
Just my opinion though.

Thank you!!! But another question, can you perhaps tell me what Yumi's feel at the end of chapter 8 and the expression he had after giving the album? I know it must not a regret since I don't think it'll suit the atmosphere(?)but I can't really tell what it is...

I think, he gave the permission for forgiveness. The album is basically a gesture from Yumi, that it is okay to move on, he is happy and it is okay to Hayashida too, if he is happy and forgive to himself. Forgiving something and forgetting something are two different things. This way, Hayashida can keep all their memories (good and bad too), forgive to himself and be with Shuuna without constan fear. Yumi relieved that someone can make Hayashida smile again, like in the old days even if it wasn't him, who did that. They know eachother that well, that Yumi knows, this helps and Hayashida has the photos. At least, I am taking in this way this whole act.

About chapter 8, I think it's clearer in chapter 9, but the beginning of the tankoubon version (chapter 9.1 here). I think Yumi Is kind of relieved that Kan-chan was almost able to keep kn going with his life, to "almost return to normal", like when Yuuna says that the room brigthens when Kan-chan smiles... I think that Yumi is surprised because during his time together, he wasn't able to see Kan-chan smile, and the fact that Yuuna brings that up makes Yumi thinks that Kan-chan is returning to his old self or kinda.
And Yumi's expression after the album par, well, I think it's just a bittersweet feeling... They went through a lot together and it's impossible for both of them to not have feelings for each other, even though not in a romantic way.
Tanaka sensei is amazing. The way all those feelings are brought to life with just a few lines and drawings... Love this work!!
Again, just my point of view, but I hope it has made thinks easier for you ;)

THANK YOU SO MUCH I LOVE YOU I HOPE YOU HAVE A GREAT DAY ٩(๑❛ᴗ❛๑)۶

Welcome! You too have a nice dayヾ(❀╹◡╹)ﾉ~