Thanks to the inclusion of not one but two so-called "Green Card" instructions, it looks as if Hibito's final test to prove his rehabilitation was about to go off the rails in a major way.
However, after a fleeting moment of panic, some rational thought of what he needs to do triggered by a look at his Pretty Dog mirror that makes for a lucky charm soon sets him straight and things quickly return to normal as he makes all of the right decisions to handle the carbon dioxide error thrown in his face by his space suit.
This isn't the end of the surprises, but thankfully from here things become far more pleasant for Hibito, as he's joined on the test by some of his former lunar mission crew-mates, not least the also recovered Damian who joins him for his "moonwalk". If Mutta is at all worried about his little brother (and thanks to some prodding by Serika he ends up sprinting to catch the end of the extended test), it becomes clear that he had no need of such concerns when he arrives to find Hibito being congratulated by all and sundry. It seems that we're now very much one step closer to reaching Space Brothers' true goal of placing its two titular brothers on the Moon together.
Although Hibito's final test could probably have been contracted down into a shorter running time overall, it was still good to be able to sit and watch his successful return to action, and the introduction of his former colleagues added to the feel-good nature of the end of a story arc that surely puts us close to the show's "home run". It's further evidence of how well the series uses its characters that it can take a story that's effectively resolved but still carry it a little further to make it even more satisfying - roll on whatever Space Brothers has to offer us next as it rolls towards its hundredth episode.