Reason to rethink managed funds? Wife nestegg shock

[marihana]

Since discovering Retire Japan last year and for the most part lurking on this forum and learning much from active memebers who know much more than I do, I've been moving what savings I have into index funds, mainly eMaxis slim all country equity and eMaxis developed country bond funds (the latter for stability going forward, given my age of 72). I don't expect that much from the bond fund, but have been generally happy with the performance of the equity fund - until yesterday, that is.
After finally persuading my wife to take more interest in investment or let me handle it, she got online access to some Mizuho Securities assets, 6 million yen that she inherited last July and allowed a Mizuho Sec. sales rep to talk her into investing as he saw fit. She opted for very infrequent snail mail reports rather than online access, having few expectations and even less interest in money matters. Well we finally got online access yesterday, and opened the lid to find the following:

So, in just 9 months, 5.8 million yen has become almost 8.9 million yen (+53%) with 2 managed funds. Maybe the timing was just right, but I was gobsmacked in particular by the "Fund Mega Tech" performance of +247.8%. I had prepared an SBI Securities account for wife and was planning to move her various assets there, but I'm inclined to leave this little nestegg as it is until I can understand it a little more. In fact, I'm having to hold myself back from buying some "Fund Mega Tech" myself. I know that management fees are much higher than index funds, running about 1.6% for both funds, but performance looks amazing.
Given the above performance, and being a dummie in search of answers, I hope to pick the collective brain here to help me better comprehend the above image and come up with good reasons to stick with index funds rather than explore managed alternatives like Fund Mega Tech (and Capital World Equity).

[Deep Blue]

The more concentrated and specialized a fund is, the more extreme the returns can be - in both directions.

Most of us realize we can’t pick these funds reliably and hence settle for market average returns at a low cost rather than thinking we’re smarter than the collective wisdom of millions of market participants and trillions of dollars worth of cash.

It is also very true that past performance is no guarantee of future performance. Cathie Wood and her range of Arrk funds had an amazing running the pandemic and have since collapsed.

It is great your wife has had a strong run in her managed fund but don’t expect this to always be the case. Megacap tech has been the best theme for a couple of years but who knows if oil or China or biotech or emerging market small caps will be the best theme for the next few years? I wish I but I don’t.

[RetireJapan]

Past performance does not guarantee future returns (in fact, it might make them less likely).

Sounds like your wife was very lucky this time.

In similar situations my parents in law were put into Turkish Lira bonds, with less desirable results.

See how that fund is doing in 5, 10 years time compared to a global index.

If you are going to need the money soon and it would make a difference, I might consider taking some profits. It would not be surprising for a fund like that to be volatile.

[marihana]

Thanks very much, guys. I get the message. I'm sorry the image didn't display, no matter how I tried.
It basically showed the 0.8 million yen the Mizuho guy put into Mega Tech now standing at 2.8 million, and the 5 million he put into Capital World Equity now at 6.1 million. Perhaps the Mizuho guy's approach is to put the bulk into a relatively safe haven, and have a flutter with the rest. It was, anyway, his decision. I take to heart your warnings about volatility, and will be watching closely. And thanks to your views, I am now more resolved to stick to index funds.