The origin of this pic might be a bit tricky to explain for those who aren't also "Patrons of Strong-Girl Art" tier members. (If you are, then you've already seen the NSFW version of this pic, I hope.)
It started with a drawing I posted back in July for that $5/month tier, a "random muscle heroine" flexing and admiring her bicep, musing "Am I weird for being turned on by my own muscles?" Because she's blonde, a couple of commenters mistook her for Tetsuko with commenting "Tetsuko-sama being turned on by her own muscles is perfectly fine!"
And that's all it took to inspire just such a drawing of Tetsuko. Now, I have no idea whether Tet-chan actually gets aroused feeling her own muscles (I know she gets aroused when others feel her muscles), but hey, makes a cool illo, ne?
Uh oh... looks like Patreon took away the ability to put download links in posts! (Unless they've hidden it where I can't find it... to paraphrase Dr. McCoy from Star Trek TMP, "You know software engineers, they love to change things!") So right-click on the pic and download it that way, I guess.