Ah yeah. I feel like SOL like Gochiusa is very re-watchable and isn't ruined at all by knowing the plot, because the value is more in the exact way the characters interact with each other moment to moment. And that I usually don't remember well. But if you remember the lines than that very part is spoiled indeed.

The first opening is really a classic and very comfy. One of the few songs where I can half remember the lyrics. Why is it a mistake to watch the anime after reading the manga?

I have never polished a razor. The most I have done is take some stropping compound and rub it on the surface with some paper towel. Personally I would be a little bit scared of the edge when it comes to the wheel. Maybe watch out for the mistakes in this video: https://www.youtube.com/watch?v=nB2Ko-u8MTk

Happy cake day!