The first row of economy is blocked by JAL for elites and paying customers (they may not be able to see your status but try calling and I believe you should be able to get it or maybe it is just for OWE).

I haven't flown this particular plane but from the schematic here: JL Boeing 777-300ER type W84 - aeroLOPA | Detailed aircraft seat plans you will have a fair amount of legroom on 23 and should be able to move without forcing the other person to leave its seat (if they are sleeping you may bump into their legs however).

On 45 that won't be an issue but you will be by the galley and it may get noisy. You also have no window here.