Getting thoughts like this isn't uncommon for /ksg/ but if you're getting them consistently it can be worth considering your mental health. Theres nothing wrong with talking to your GP/doctor/therapist about these thoughts and you don't need to have a mental illness to make talking to these people a good idea, talking to a professional and building a support network is often the first step in improving your life when these thoughts start to become a burden. Things like taking up a communal hobby or exercising can also be a great help in improving your life.

While you may not physically be able to date Emi or any other Katawas girls like them exist and theres no reason why you can't find one, one of the key points of /ksg/ is that the main cast (and people with disabilities in general) are just normal people that exist and you can find in real life. So get out there and find her!

If you feel suicidal or need to talk to someone please consider contacting your regions suicide or support hotline
http://www.suicide.org/hotlines/international/united-kingdom-suicide-hotlines.html
http://www.samaritans.org/
https://suicidepreventionlifeline.org/
https://www.reddit.com/r/SuicideWatch/wiki/hotlines
You're not the only one who's been there and just talking to someone who won't judge you and will listen can massively help.

Other helpful resources for those struggling with their state of mind
http://www.nhs.uk/Conditions/stress-anxiety-depression/Pages/low-mood-stress-anxiety.aspx
https://www.mind.org.uk/information-support/types-of-mental-health-problems/depression/
http://www.mentalhealthamerica.net/finding-help
https://www.reddit.com/r/SWResources/comments/1c3p3z/helpful_resources_for_those_struggling_with/

Written for Mental Health Awareness week and the recent uptick in posters with these thoughts.