Concerns about Sharon's health couldn't really come at a worse time, arriving as they do literally right before an important exam for Mutta - an exam that he struggles to concentrate upon at all.
With Mutta's results proving to be an abject failure on account of his wandering mind, unfortunately there isn't any happier news in terms of Sharon's diagnosis - although doctors can't immediately pinpoint the neurological issue that she seems to be suffering, Serika's suggestion that it could be amyotrophic lateral sclerosis (aka motor neurone disease) rings true with those doctors, and lo and behold further testing confirms that she does indeed suffer from this incurable neurological disorder.
Although Sharon puts a brave face on things as she returns to Japan still confident in her ability to complete the work she needs to carry out regarding her plans to build a telescope on the Moon, Mutta is left feeling despondent and wondering whether he'll make it to the Moon on time to play a part in achieving her dream, especially given his recent test result. Unable to even find any comforting words to cheer up his "aunt", it takes an old anecdote about Sharon from his youth to allow him to find the phrase that he needs.
There really isn't a whole lot to say about this week's Space Brothers other than to repeatedly use the phrase "relentlessly depressing" - it's certainly a spot-on treatment of dealing with the diagnosis of incurable illness for a loved one, but it's such a joyless subject that it's hard to get enthused about it. It's great to see an anime series tackling a real-world disease in this way though (and let's be honest, it's quite a rarity), so maybe if it encourages just one person to be diagnosed quicker with a similar disease then perhaps there's more to be said about this episode than simply its ability to afford some extra drama and to ramp up the importance of Mutta's goals.