This my theory
1. Why future man say will save chiho?
2. Maybe he already know chiho pregnant and that will make human evolution to next step like human from future
3. Maybe chiho pregnant because of him, that he say will save chiho. Why chiho not notice? maybe he used some trick from that tool that make chiho not notice
4. Human from future not know about sex? maybe he already watch chiho jav already
Note : Does not rule out there will be ntr