Whom to ascend - GM or Mitsuko?
First priority is offense in the team with Grazul, Marjana, Boldtusk and Guardian falcon. Second priority is in defense which currently looks like Kage-RED-Tella-Vela-Joon
Having tested both on 3-70 I am likely to choose Mitsuko - to use shilelds against Vela, who is often in defense now. She will also get family bonus with Kage in defense.
Are there any agreements to ascent GM instead?
Mitsuko has a very specific use and she is better than anybody for it. That being said, GM is absolutely better overall. If Vela falls out of fashion post nerf I think you may well regret maxing her ahead of GM. Vela is not, of course, the only hero Mitsuko addresses, but she is a fair bit more common than other really problematic blue on D, Finley.
Tough call. Both are great on offense and defense. Mits is more specialized and can neutralize blue strikers, the mana drop is welcomed too. GM is all-purpose killer, good anywhere in defense and can be used against about any team…strong DOT. GM has the lead in my mind but Mits is nothing to ignore.
^ I agree with both. That said, gm all the way
I presume this is a joke question?
Why anyone would even consider ascending mitsuko over GM is surely having a laugh.
Grave.
Mits is a game changer against Finley and vela (primarily)… IF you can get her to charge. You’ve got two average mana heroes already with bold and falcon… you don’t want a third.
Grave is just… grave. Solid in defense. Solid in offense. Just a beast.
I hate when I find typos after the fact.
Well, both based on a gut fill and on calculation of damage dealt per 3 tiles of charge - GM is stronger.
But I have tried several times with GM and Mits- and found that statistically I win more often with Mits. This is indeed caused by Vela. But that is what we have now.
As for the speed - Boldtusk charges with 9 tiles (talents, suit) and Mitsuko after Grazul ultimate ability and her element link (mana speed) also charges with 9 tiles. So specifically in this offense team and against Vela flank - Mitsuko seems to be stronger.
Obviously GM is better in defense. The only issue - his class Rogue - same as Kageburado who also is in defense team.
And GM is better in 3+2 teams. However I think 3+2 is preferable when you have almost all heroes 5* for attack. This is not my case yet and I play mono, thus this is the team that the candidate had to fit into.
Anyway - I may be mad, but I chose Mitsuko… Hope Vela will stay on the flank of a green center 
Listen to the teacher.
But also, save your rings and ascend mits next. I use both constantly.
You’ll enjoy her!! Then you’ll max grave and ask yourself why you waited so long! Lol
Your game. Your decision. Just have fun.
To me, they are both useful, but it really just comes down to speed. At Very Fast, I couldn’t pass up Gravemaker.
I actually had just ascended Mitsuko when GM came along at the beginning of this month. Fortunately, I had extra rings available because Mitsuko was only my second-ever 5* Red after 18 months of playing, so I was lucky enough to still have 6 rings left when Gravemaker popped out of the portal for me. 
That said… progress on Mitsuko abruptly stopped at 4-19 as soon as I got Gravemaker. He is now 4-42 and I will resume Mitsuko’s rise to max after GM is maxed.
Good gaming!
Congrats on pulling him!
Gm is a beast but mitsy is extremely useful against blue flanks and wings…she is awesome too.
#mitsybluekiller