i don't exactly follow the first panel on the 3rd page. did Tatsuya release the sleeping gas on his way down? but even if he did, why does the second sentence "it looks like i made it in time" seem to impose him being late on his return? or did he even consider his initial duration of climbing down and his encounter in that thought process? i guess then, it would make sense.
on page 17 the 2 lower sentences in the second panel (upper left) also slightly sounds weird.
as for the plot, it's kinda rare, but seems like tatsuya did not finish his mission perfectly this time around which comes as a pleasant surprise.