Shinjiro knitted Aki’s red scarf. He knows red is Aki’s favorite color. He also gave him some stuffed animals and other toys with the intention of dedicating them to Miki in her birthday (Aki was supposed to keep them though, and he did.)
They didnt have money for books while in the orphanage (elementary and middle school), but Aki always cared about keeping good grades and being a good student, despite trying to pretend he didnt. Shinjiro picked up on that. And at some point, just showed up on their room with a bunch of books. Shinjiro was the first to start working/having part time jobs. So Akihiko was never really sure if Shinjiro bought those or stole those. And he doesnt ask. So basically, Shinjiro gave Akihiko most of the oldest books he has.