@MarqFJA87 It might be a bit ambigous, but the original text on the bottom of the second page was an euphemism for... well... that they had sex.
Originally I think page 2 meant as a reference/parody on something, but then Os_fresa added another picture to it (page 3) and while not expained at the post, but to some comments asking, sensei said "Souta climbed the ladder of adulthood."
The 1st picture was actually in a different post at a different time originally, and it was explaining something about drawing backs (hence the red arrows (there was no text next to the arrows on the picture though. that was in the tweet)), but tematically it belong here, so we included it here.
And, the character introduction extras did said Nei might will do something if Souta is in front of her when she's in her true form not surpressed by the eyepatch at all...
Anyway, cute, cute Souta-kun lost something for good, never to be found again.
that is... his virginity XD