It should be studied how Riku is able to sleep through literally everything. I thought it'd be explained a bit but no, the boy is just in a constant state of being half awake. The extra chapter was bitter, cant even call it bittersweet since so much of it feels unsatisfying. There's the author's message at the end which I'm waiting for someone to better translate, but the author admits his own weak writing and promises he'll apply everything he learned to do better next time (which he says he's already started on).