Decided to switch gears to team Minoriko, the team that last beat up Maribel. First I beat up Beast of Centaurea without any difficulty, and then moved on to try out some of the V2 bosses (only managed Chen and Reisen V2, the other did too much damage). I then went to try boss rush, but ran into considerable TP issues, which isn't terribly suprising given this team's issues with trash cleaning endurance. I grinded up to Mino 135 for my next try, which got me all the way to Maribel with an almost TP dead party. I got her down to her last phase, and then: Overflowing Unnatural Power -> Hypderdimension Flying Object -> Djinn Storm -> Hyperdimension Flying Object. She ends up using HFO a lot in the fight and suffice to say, I didn't win.
Dejected by my horrible luck, I grind up another 10 levels to Mino 145. This time, I reach Mari with a rather TP healthy party (partly in thanks to adding more SKP levels into TP, and partly in being 10 levels more powerful). I got her down to her final form with little problem again. However, she happens to follow her self buff with HFO yet again, which spectacularly one-shots a 100% DEF-buffed Tenshi for around 14.5k damage in slot one yet again. I switch Remi into slot one to replace the fallen tank, only for Mari to whip out another HFO, one-shotting Remi yet again. It's now up to Ran to take up the 1st slot tank role, and thankfully she doesn't use HFO again for the rest of the battle, so I eventually take her down. I've never had such issues with the Boss Rush before, nevermind Maribel.
I then resumed grinding 20F to fill out the items on the first 10 pages. While grinding, I found: 1 Karen Device (yay), 2 Armads, and 1 Divine Spirit Barrier. Still need the Flower Blade and Scourge.
EDIT: Beat all the V2 bosses and all Blood Seal bosses. I still need to find the last two 20F drops, but I can go explore 21F now! Hibachi was taken out at Mino 166, Bloody Papa maybe a level or few higher, and Dual Hibachi at Mino 180. Bloody Papa was surprisingly easy given that both Tenshi's Sword of Rapture and Maribel's debuffing attacks failed to reduce his magic even once during the fight. However, Cirno's SPD debuffs worked perfectly to slow him down enough so that Remi and Rinnousuke could plow through his HP. Hibachi was a bit more challenging with Needle Parade being a death knell for poor Mino, but aside from that not that bad. Dual Hibachi was quite a pain, however. It was only after several attempts that I finally defeated them. It was still a very close battle, though. I started by wearing down some HP on Hibachi 2 while buffing the stats of my characters with Rinnousuke and Ran. Once my team was all buffed up, I dealt about 900k HP on Hibachi 1 before switching my focus back to eliminate Hibachi 2. Marisa gets to fire off a quick 300k Spark and switches out before Hibachi 1 gets a chance to attack. Ran switches in to shave off 60k with Fox-Tanuki (Kanako and Mari already died, unfortunately), and then Hibachi 1 launches a Needle Parade, leaving Tenshi and Remi in the front two slots with Marisa and 3 death fodder in the back line. Before getting a chance to switch Marisa in for another attack, Hibachi followed up with its Washing Machine, wiping out Remi. Tenshi then fell to a Kanon after switching Marisa in, who finished the battle with a 200k Spark.