Understanding 「いたずらもここまで手が込んでくると まあまあかな」

Question

From the first episode of Death Note, the main character ponders some crazy claims made in a notebook he finds. He eventually mutters to himself:

いたずらもここまで手が込んでくると まあまあかな

Literally speaking, this seems to mean something like:

As for whether this is also a prank, if up to here it's complicated, then "my, my".

But I'm pretty sure I'm not parsing right because it doesn't seem to quite make any sense. Is there a better way to translate this sentence (while keeping the Japanese translation as literal/close to the Japanese as possible)?

Ultimately, I'm assuming the sentence translates to something like:

If, up to here, this has just all been a complicated prank, then ... "my, my".

But I don't see how the sentence is quite conveying this, grammatically. (And as I side note I don't understand why も is being used after いたずら, instead of は).

Answer 1

There are several key issues here which I thought were interesting and may not be straightforward. I will give you a breakdown.

• も

"even" I feel this も stresses the topic.

いたずらも: Even as a prank

• くる

As @aguijonazo points out this くる is defined as (デジタル大辞泉（小学館）):

９ （補助動詞）動詞の連用形に接続助詞「て」が付いた形に付く。

㋐少しずつ移行したり、程度が進んだりして、しだいにその状態になる。だんだん…になる。「日増しに暖かくなってきた」「最近太ってきた」

• 手が込んでくる

Therefore, here this phrase means "intricately/elaborately crafted/devised"

• と

I would think of this と as "when" rather than "if".

• まあまあ

means "not too bad"

Thus

いたずらもここまで手が込んでくるとまあまあかな

means:

(Even) as a prank, it is not bad when they put so much effort into it

Answer 2

The structure is

いたずらもまあまあかな

where the following conditional is inserted

ここまで手が込んでくると.

The former means

Prank is okay as well.

and the latter

if (it is) contrived this much.

You should be able to see the meaning simply by combining these.

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BTW Weblio does seem to say my, my is まあまあ, but I suppose it is in the sense of emphatic まあ (Wow). which seems consistent with "interjection An expression of surprise, incredulity, or pleasure."

The まあまあ here is so-so (#3)