This reminds me of the Doumin Seiman story about the guy who gets a job at a convenience store. On a native american burial ground. And then dies? And then turns into a robot. And then a girl?
@someguy1 that manga was great. I laughed so hard when the love interest girl just causal responds to MC's worries about their sex with "It's cool. I swing both ways" at the very last page.
Só, he first became small -> Good for stalking
Then, he became a girl -> Nobody will raise suspicion, good for stalking
Finally, he become invisible -> The supreme stalking power, he problably is happy