So being new to the series actually helps you...You can’t grab the tadpole and dangle off the edge in previous games,and there was no HP bar as well,any body contact with enemies and you fail.This game is a lot easier to beat at least.
I guess having a new perspective helped! It turns out you don't need to throw the fishing line over and over again against the boss, keeping the line hooked in will slowly drain down its health even if you get hit. So if you grapple on and dangle over the ledge, you can deal a lot of damage while being safe from the fish. I keep my line on the boss as it jumps up, then I get hit but I get to the left of it. Keeping the line on the tadpole as long as I could, I was able to bring down the time to 23 seconds in both Time Attack and Challenge mode. Just make sure not to get hit while being over the ledge. Even if you deplete all of its health, you will still die if you run out of health or fall off the ledge when the boss has no health left.
Also, here are my times and the history of them in the demo so far. I might make videos of these later. I referenced these from screenshots I took over the course of this week. Some of the levels I have not played much so they might be too slow, and also since this is my first Kawase or fishhook game of any kind it's hard for me to play. But, I was able to bring all but one of my times under a minute!
Time Attack:
Quest 1: 21.35 3/29, 23.80, 24.21, 25.41, 27.88, 28.21 3/28
Quest 2: 47.50 3/28
Quest 3: 8.50 3/28
Quest 4: 22.73 3/29
Quest 5: 18.21 3/30, 18.63 3/29
Quest 6: 26.33 3/29
Quest 7: 54.51 3/30, 1:26.05 3/29
Quest 8: 54.08 3/30, 1:28.31 3/29
Quest 9: 1:03.83 3/30, 1:42.50 3/29
Quest 10: 56.06 3/30, 1:19.88 3/29
Quest 11: 45.50 3/31, 51.65 3/29
Quest 12: 23.55 3/30, 40.83 3/30, 58.81 3/29
Challenge:
Challenge 12: 23.78, 25.31 3/31, 34.96 3/30, 1:32 or 1:36? 3/29
Sum of Time Attack times: 7:22.15 3/31
Sum of Time Attack + Challenge times: 7:45.93 3/31
Now here I am proud to present beating the demo in under 12 minutes from the start of the first quest to the end of the last quest, 11:57 real time and 8:33.99 in-game time. After playing Time Attack some I thought I would speedrun the full demo on fresh save data. I am having a hard time learning the techniques (as you can see I don't use Rocket Jumps and move slowly through the levels) but no one else has speedrunned the demo on YouTube yet, I think. Also after 6 attempts I got my first run with no death, hooray! Earlier today I got a 14:42 and 13:21 but they had so embarrassing deaths and mistakes. This run went pretty well I think except for the complete fail on Quest 5. Sorry for some recording issues in the middle. Even with my bad playing hopefully you all will enjoy the new game in a speedrun!
https://www.youtube.com/watch?v=ztzdZuKTWR0