Too Much of a Survivor!

"Control or fusion?"

Shinji was taken aback, then immediately realized that the Susanoo Lamp seemed capable of bypassing the surgical process and using a Dojutsu to fuse the power of two pairs of eyes.

At the same time,

he understood that controlling with the Susanoo Lamp and fusing were two separate things.

They were completely different concepts!

Control.

This meant using a second pair of empty eye sockets to hold another pair of eyes, thereby gaining some of their power or some of their Dojutsu.

That was the state Shinji was currently in.

Normally, while controlling a second pair of eyes, it was impossible to obtain their full power.

This was easy enough to understand. After all, they belonged to someone else, so some degree of rejection and resistance was inevitable.

As for how much power one could obtain from a second pair of eyes, that depended on the strength of one's own eyes.

For example, even though both pairs were Mangekyō Sharingan, Shinji could only barely obtain fifty percent of the power of Fugaku's Mangekyō by controlling it with his own.

If Shinji himself possessed the Eternal Mangekyo Sharingan, then he could obtain seventy percent of the Mangekyō's power by controlling it with the Eternal Mangekyo Sharingan.

Going a step further, if he used the Rinnegan to control a Mangekyō, his overwhelming advantage might let him draw out eighty or even ninety percent of its power, coming close to fully controlling it.

Fusion.

As the name suggested, it meant combining two pairs of eyes into one and fusing their powers. Once complete, only a single pair of eyes would remain.

All fusion came with some loss. That was only natural.

For instance, Sasuke had fused Itachi's Mangekyō Sharingan with his own in the original timeline and successfully obtained the Eternal Mangekyo Sharingan, but he hadn't perfectly inherited all of Itachi's Mangekyō Dojutsu.

Tsukuyomi had been lost in the process.

So fusion through the Susanoo Lamp had its limitations, too.

However, the Susanoo Lamp had a unique trait: the amount lost during fusion was determined by the strength of one's own Dojutsu.

Fusing a Mangekyō with another Mangekyō could result in losses similar to those of surgical fusion, and there was a good chance the fused Mangekyō's Dojutsu would be lost.

If one's own Dojutsu was weaker than the other person's, the fusion might even fail.

But if one used the Eternal Mangekyo Sharingan to fuse with a Mangekyō, the losses would be smaller—just barely within acceptable limits.

By the same logic, the stronger one's eyes were, the less would be lost in fusion.

If one's eyes were strong enough, it might even be possible to try fusing them with eyes from another Kekkei Genkai, such as the Byakugan!

After understanding all this about the Susanoo Lamp, Shinji didn't rush to decide. He first deactivated Susanoo to avoid wasting his Dojutsu, then sat quietly in the cave and thought it over.

Judging by the Susanoo Lamp's properties,

the stronger one's Dojutsu, the more options one had. That was true whether controlling or fusing!

So from that perspective, strengthening his own eyes was the best choice.

Shinji had also realized that controlling Fugaku's Mangekyō Sharingan had greatly increased his own Dojutsu, pushing it beyond the level of an ordinary Mangekyō.

But he still couldn't replenish his Dojutsu by refining Yin Release Chakra himself.

In other words, the strength of his Dojutsu now fell below that of the Eternal Mangekyo Sharingan, but above that of an ordinary Mangekyō Sharingan.

"Looks like fusing them into the Eternal Mangekyo Sharingan first, so I can replenish my Dojutsu on my own, is the way to go!"

Shinji had a plan, but his expression was grave.

After using the Susanoo Lamp to control Fugaku's Mangekyō, he hadn't just learned a great deal about the Susanoo Lamp. He'd also gained considerable insight into Fugaku's Mangekyō.

One detail in particular posed a serious problem.

Fugaku's Mangekyō actually had more Dojutsu than his own!

In other words, he was currently trying to control a stronger pair of eyes with a weaker one!

"He awakened his Mangekyō seven or eight years ago, yet he's preserved more of its power than I have in this fresh pair I've had for only a few weeks. How has he even been using it?"

Shinji was speechless.

He knew he'd been using his Mangekyō Sharingan pretty recklessly lately.

But Fugaku had awakened his Mangekyō Sharingan during the Third Shinobi World War, which had been before Sasuke was born.

After all these years, he'd still preserved so much more power than Shinji.

"That's an incredible level of caution!"

The Susanoo Lamp's judgment couldn't be wrong. So after awakening his Mangekyō Sharingan, Fugaku had hardly ever used its Dojutsu.

He might not even have activated Susanoo once in his entire time as a Mangekyō Sharingan wielder.

Shinji furrowed his brow slightly.

The moment he considered fusion, the Susanoo Lamp had already given him a warning.

Trying to control stronger eyes with weaker ones meant the fusion was highly likely to fail!

That also made him understand why, throughout the history of the Shinobi World, every successful case of fusing into the Eternal Mangekyo Sharingan had involved blood relatives.

Whether it was the brothers Madara Uchiha and Izuna Uchiha,

or the brothers Sasuke Uchiha and Itachi Uchiha,

it was always the same!

Only blood relatives, whose bloodlines were intertwined, could blur the difference in strength between two Mangekyō and prevent them from rejecting each other.

Although Shinji and Fugaku were members of the same clan, they weren't blood relatives.

The Chakra traits rooted in their Kekkei Genkai were clearly different, so Fugaku's Mangekyō instinctively resisted fusion.

If the difference in strength were reversed,

the Susanoo Lamp would let Shinji forcibly fuse with Fugaku's Mangekyō.

But right now, Shinji's Mangekyō was weaker than Fugaku's, so the Susanoo Lamp could only help him control Fugaku's eyes.

Shinji closed his eyes and silently felt the state of his own Mangekyō.

In fact, controlling eyes with the Susanoo Lamp also counted as a mild form of fusion.

Just now, the instant he took control of Fugaku's Mangekyō, the Dojutsu his own Mangekyō had lost had partially recovered, stimulated by the outside influence.

He estimated it by feel.

With both pairs of Mangekyō under his control, his Dojutsu was now roughly one and a half times what it had been at the beginning.

Since he didn't know whether the recovery that occurred when he first controlled the second pair of eyes could happen only once or be triggered again later,

he couldn't tell whether he now had a limited ability to recover his Dojutsu.

At the same time,

perhaps because Shinji's own Dojutsu slots were barely occupied, he'd been lucky enough to obtain both Mangekyō Dojutsu contained in Fugaku's eyes.

The Dojutsu in the left eye was, unsurprisingly, Amaterasu.

From this, Itachi and Sasuke both having Amaterasu seemed to be due not only to the way the Sharingan reflected the heart, but also to the inheritance of their bloodline.

But when Shinji learned what Mangekyō Dojutsu Fugaku's right eye contained, his expression suddenly turned strange.