Poor Takamatsu, her first ex made a huge mess, long distance relationship with a huge emotional build-up then dumping her, she went down the spiral of needing something to fill her depressed life.
Yokoi should wingman her someone who can stay by her side, as much he does with Saitou.
Now to the main course... saying "yes" would make him a bit of a creep, "no" would cause Saitou anxiety attack, but farting in the bag isna win/win