I actually bought that too, but unfortunately it won't work since one of the females from the Y-split only have three cables, and it dosen't match the once you need from the original cable.
I forgot that i actually taped everything together in an ugly hidden mess, so I'm afraid that the pictures won't help really.
Two things that will make your live easier when installing the rear cam though:
1. Buy spare blue clips, it's very easy to break them when removing the rear trim pieces. SC has them, or you can go with these: https://www.navringar.se/plastclips/toyota/plastclips-pl-2064
2. Sand down the rear cable, making it a bit smaller, round and much easier to pull it through tight spaces.
3. Skip the middle clip of the right side trim panel and pull the rear cable through there, instead of going the whole way round the trunk as daerik does. Then you don't have to remove that big trim piece.
If you're lucky, you can pull the cable trough that tiny space that's along the top trim piece in the top of the trunk, but the cable gets stuck very easliy. Mine did, and it was a pain to set it free.