Not sure if this was linked yet, but (left-leaning) twitter analyst @miraisyakai published their ratings of all the prefectural seats. In reality there are two types of prefectural seats: the multi-member seats where the opposition can usually get a seat, and the single-member seats in smaller prefectures where they get wiped out. Note that I used "smaller:" there is serious variance in the population of single-member seats, from 2.3M in Miyagi to 790K in Fukui.
Let's look at the single-member seats first. Abe's LDP swept these when the seats were last up in 2013, getting 29/31. Redistricting meant there are now 32 instead of 31:
https://twitter.com/miraisyakai/status/1152408064684744704This graph aggregates seat projections from the national newspapers, plus projections from local papers, into a rating on the far left. The "safe/lean" seats would be Okinawa, Nagano and Ehime.
The "tilt/toss-up" seats are Akita, Yamagata, Niigata, Miyagi, Shiga and Iwate. In this setup, the next closest seat (Aomori) looks like a "tilt LDP" rating. So anywhere from 4-9 seats are possible, and those are the seats to watch.
With the multi-member districts, the most interesting ones are those with an odd number of candidates, since inefficient vote-splitting between a camp's candidates can squeeze one of them out for the last seat. There are the LDP/JCP duels for the third seat in Hokkaido and Chiba (the Hokkaido one not being too likely), and a battle between CDP and KP for third in Hyōgo. JCP is also looking for the fourth seat in Osaka versus KP.
JRP/Ishin no Kai may or may not get the last seat in Kanagawa and Tokyo, squeezing out JCP/CDP candidates respectively. There's also 2-member seat Hiroshima, a stalwart right-wing prefecture but will face vote-splitting from two LDP candidates versus an opposition independent. Kyoto also has a face-off between the JCP and CDP candidates.
