Indoor bouldering is done on short walls, usually max 4m high, and without ropes. The floors are heavily padded - think the same mats used for pole vault landings. Seiichi just doesn't know how to be a good spotter.
Is linking to the raw - which is already linked on the description page - a spoiler? It's not like any of its contents were discussed. I've been reading them, but was going to wait for the translated version before saying anything about them here.