Shizuna [Limited, Debut]
No one in particular worth rerolling for. If you want to do Advanced Rerolling, choose Erica-Chaldea(Neno)-Ariel in Rookie Sprint and reroll for either Erica or Chaldea.
Simple Rerolling (Don't start with limited units): Same process as always (Link to guide)
Advanced Rerolling (Start with at least 1 limited unit): Use the Advanced Rerolling guide (Link)
Shizuna should be skipped.
RTA has ended, and ML5s that were only good in RTA (especially Gagarin and Diva) should not be pulled in the Mysterious select banner.
Successor Mikael (Boss), Radiant Rubi
Neither bosses deal much damage, and Rubi can be neutered by applying DEF Down.=
Nothing worth talking about, you can bring your Red Hunt team or simply bring 4 non-fire DPS.
Featured unit: Odea
Odea is not useful. She works as an AOE opener in low ranks but is held back by her extremely low base speed and poor utility.
Buy for Rainbow value or skip.
E7: Ludwig
Shizuna is a nuker who can strip, stun, and turn herself invincible.
Shizuna's skill chain is S2 > S3. S2 is a single target attack that attacks, decreases buff durations by 1, stuns, self-buffs Invincible and ATK Up, and self-pushes 50% (in that order). The buffs being applied after the attack is a small downside. S2 can be soulburned to ignore RES.
S3 is an AOE that penetrates up to 60% DEF, and if the skill kills any enemy, extends self buffs by 1 turn, which naturally extends her Invincible.
Her S1 can steal (Strip & Copy at the same time) 1 buff from the target, and self-pushes.
Importantly, S2 does not generate an extra turn, but rather grants a measly 50% self push, which means that she can't truly chain her skills on her own. She must wait her turn before she can follow with S3.
Shizuna has the highest base ATK of all units so far, and that helps her deal fairly high damage if fit correctly. She can use S2 to stun and heavily damage a threatening unit, then (if she can get her next turn) follow up with S3 which can kill one or more units to maintain her Invincible.
An example build with 3.3k atk and 300cdmg shows 8~9k for S2 and 14k for S3 (w/ ATK up and Invincible) which is a lot of damage.
Her deck thinning power is very low, her skill chain is lackluster, and her utility is dubious. There are many units that perform similar roles as Shizuna but have proper skill chains and more utility. Many such units that are currently meta have an off-turn self-push to help grab their own turn (Layla, Gail, and more) or have team gauge pushes to boost the whole team's tempo (So many examples...) while Shizula struggles to even pull herself up.
Very low base speed of 112 makes it hard to build her fast enough.
Being a Green element, she struggles against Red element units, and she doesn't have helpful "tricks" like Base Accuracy or Guaranteed Crits.
Build as a standard high-speed nuker with Speed / Destruction + Crit / Pen / Riptide. Right side CDMG + ATK% + SPD.
Bringing Book (Flutter) allows her to soulburn S2, which is better value than mere damage bonds.
A high-speed opener build is possible especially if chained with Dawn and Anh, but is ill-advised due to Shizuna's low base speed of 112.
Building for RES is possible to protect her Invincible and improve her staying power, but this doesn't hold much merit as she fizzles out after S2 > S3 and has little to no advantage towards staying alive. She shines in cleave comps where the battle ends quickly.
As for team comps, Shizuna struggles to perform on her own and must be combined with units who can grant her tempo. Yuri is an especially strong combo as her Blink buff (which is guaranteed to happen if Shizuna soulburns S2, which fulfills Yuri's S2 conditions) can give Shizuna +50% more gauge push giving her 100% total for a faux-Extra Turn effect.
Any other unit who can react to her S2's high damage (Gail, etc) or its debuff application (Layla, Dawn, etc) can work also.
Shizuna bond: Not even Shizuna herself uses this. Skip
Layla bond: Good, but not worth having multiples of.
CBerrica bond: You only need 1 copy to get the ACC bonus which is the most important aspect of this bond. 1 copy needed if you have CBerrica.
Kumone bond: A decent brawler bond, but slightly worse than both Aoi bond which has a direct damage bonus but only heals for half as much, and SSJ's bond which buffs crit rate instead of ATK.
Riria bond: Also useless.
4* Apathy bond: If you're a new player who has Chaldea but not her bond, get 1 copy of this for her.