In this instance, pick Lozenge Magus. Not only because of the effect of being called to the Rear Guard, but the "return to Deck" part of it, which makes Heal Triggers in this deck reusable.
The main strategy of this deck is to make the Soul have less than 1 card. (Yes, I mean 0 cards or 1 card depending on circumstances) for Scarlet Witch Koko to use her effect to the maximum efficiency. Such cards that use Soul Blasts are as follows:
Unfortunately, there's not enough Soul Blast effects that can stand out in Oracle Think Tank, so an alternative strategy was needed.
The alternative strategy is to use CEO Amaterasu. Using her Soul Charge to check the top card of the Deck almost guarantees for a Trigger. Also, her effect for a power boost only requires that you have 4+ cards in your Hand while CEO Amaterasu is in the Vanguard Circle. Also, with her Soul Blast 8, Counter Blast 5 effect, you can drain your Soul well enough to call Scarlet Witch Koko and use the effect to the maximum.
Such card(s) that can be added to Soul are:
With 16 Grade 0 Shields (10000, unless it's a Draw Trigger, then it's 5000) and 11 Grade 1 Shields (5000), you can guard easily from attacks. Also, with Security Guardian intercepting (It becomes 10000 when intercepting, otherwise it's 5000.), you have 8 other Grade 2 Interceptors/Guardians. If you use Battle Sister Chocolat as a Guardian, you can discard a card to block an attack completely.
Sample Deck List:
4x Psychic Bird
4x Dream Eater
4x Luck Bird
4x Silent Tom
If you have any questions, leave a comment.
Also, I noticed the random "spaces" between randomly that I didn't expect in "Cardfight!! Vanguard - Strategies - Kagero - Part 2", so I took some time to repair that post as well. Sorry for the inconvenience from that.