User blog comment:B214/Volume 23 discussion blog/@comment-86.143.86.100-20170203180136/@comment-95.233.181.246-20170204015837

I doub he would train his demonic powers. Demonic powers are not like body, which can be trained so much. Demonic power comes from talent and blood, and Issei demonic power always sucked from the beginning (and Ophis and Great Red did not change it because they are not demon). So I think it would be useless for him.

But he could do an overwhelming training like Sairaorg did, and with the power of Boost he could train for weeks without a pause (for example each time he used half of his physical energy, he could use Boost to return to his full usual energy). This way he could become very stronger in a short time.

Because Issei has really to improve is normal powers. For example with the simple Scale Mail I guess he is still the weakest Sekiryuutei ever existed (I'm referring only to his normal balance breaker). Buf if he would train to improve his body even near to Sairaorg's level, his power would increase dramatically. He could Boost much more and with a power up several times stronger than now (if in his base state his strenght is 10, he needs many boost to reach 1000; but if his base strenght was 100 it would be already an incredible improvement). Even because his body has to sustain his boosts.

So I guess that right now he has to stop and think to the fundamentals instead of reaching others powers with his dragon's powers. He has to complete himself alone before doing so or he will never be able to achieve his own perfection as a fighter.

When he will have done it, he could think to Dragonification (that with a base strenght of the higher level would be incredible).

And then think to an Abyss Break. He has to develop every quality in which he has great possibility of improvement. In cases like his, a step back is the best choice.