Hikari's first Artifice is her Opening Act, which deals 1098% damage to your front 3. It cannot be evaded.
Her two minor Artifices are her Ending Act, which stuns your front 2 units every other turn, and the special targeting on her normal acts, which deconstructs your team from back to front, leaving you unable to take advantage of a tank to soak damage.
Note that every single move in Hikari's arsenal can be taunted, which greatly reduces their impact.
For her Opening Act, a girl that has a passive taunt at the start of battle will redirect all the damage to only that girl, leaving you with all other members at full HP to battle.
For her subsequent attacks and stuns, a cloud tank that has redirecting moves on normal acts will work. Hikari's normal acts costing 3AP and only targeting one unit mean that she can only attack twice per turn, giving her the lowest regular damage output of all Challenge Revue bosses.
Alternatively, use three fragile unit skill sticks without fortitude passives to eat the opening act and die, leaving you with two healthy girls to kill Hikari with.
I am now obligated to share this guide, drawn up by TMuki#4504 (muri), since it is both informative and a glorious work of art.
Refer to the video example here.
Without a 4β Cloud Tank
Employ the use of multiple 4β cloud girls. The US21 Musketeer Hikari and Musketeer Karen you obtain from ad-gacha are extremely useful. Awakened Fumi, Ichie, and Yuyuko are all strong contenders to be included as well, as is Bride Hikari, Kung Fu Mei Fan and Robin Hood Junna. and 3π Greenhorn Helmsman Misora
Slightly less ideal picks include other 4π clouds who lack a single-target damaging CX, such as Greenhorn Captain Aruru, Genie Tsukasa, Sherlock Hikari.
Due to the nature of Hikari's secondary Artifice, ensure that your two most damaging attackers are the back two, as your front two will be stunned half the time.
Sample 1
With a 4π Cloud Tank (Taunt)
Compose a team consisting of the taunter, a cloud tank, and one strong cloud attacker. This enables you to taunt every other turn and fill up all remaining AP with the attacker's moves. This is simple, fast, and reliable. Do not place any fortitude on your passive taunter so as to avoid their moves from clogging up your turn 1 hand.
Fastest Reliable Team
3 turn completion. Use 30% defensive and as much offensive US as possible.